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the  ^Journal  of  the  Society  of  A*.   ." 


NE\V  Yv/RK: 
I  XObTiiAND,    PT  BLISHEK, 

I    'i ;  37  S'/AxiitEN  STREETS. 

1  8  v°  7 . 


THE  VAN  NOSTRAND  SCIEN1 


18mo,  Grceen  Boards.    Price  50  Cents  Each. 

lustrated  when,  the  Subject  Demands. 


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5AT1ON.     I 

Prof.  W.  H.  Corfield. 
No.  19.— STRENGTH  OF  BEAMS    UNDER   TRANSVERS 

LOADS.    By  Prof.  W.  Allan. 
No.  20.— BRIDGE   AND  TUNNEL  CENTRES. 

McMasters,  C.  E. 
No.  21.— SAFETY  VALVES.    By  Richard  H.  ] 


THE 


TREATMENT 


SEWAGE. 


Dr.  C.  MEYMOTT  TIDY. 


\Abridged  from  the  "Journal  of  the  Society  of  Arts: 


NEW  YORK: 

I).  VAN  NOSTRAND,   PUBLISHER, 

23  MURRAY  AND  27  WARREN  STREETS. 

1887. 


THE 

TREATMENT  OF  SEWAGE. 


LIQUID  EXCRETA. 

Every  adult  male  person  voids  on  an 
average  60  ozs.  (=  three  pints)  of  urine 
daily.  The  60  ozs.  contains  an  average 
of  2.53  ozs.  of  dry  solid  matter,  consist- 
ing of — 

Urea 512 . 4  grains. 

Extractives  (pigment,  mucus,  uric 

acid) 169.5      " 

Salts  (chiefly  chlorides  of  sodium 

and  potassium) , 425 .0      " 

1106.9      « 
=2.53  ozs. 

The  urine,  therefore,  of  a  population 
of  10,000  adults  may  be  taken  as  600,000 
fluid  ozs.,  or  3,750  gallons  per  day. 

Urine  rapidly  decomposes,  the  urea  be- 
coming the  volatile  body  carbonate  of 
ammonia,  and  the  urine  thereby  losing  a 
valuable  manurial  constituent.  After  a 


time,  but  at  a  later  stage,  certain  foul 
smelling  gaseous  products  of  decomposi- 
tion are  evolved.  To  collect  and  preserve 
urine,  therefore,  presents  practical  diffi- 
culties. The  ammonia  from  stale  urine 
was  formerly  distilled  and  converted  into 
a  sulphate,  at  Courbeville,  near  Paris. 

SOLID  EXCRETA. 

Every  adult  male  person  voids  about 
1,750  grains  (or  4  ozs.)  of  faeces  daily,  of 
which  75  per  cent,  is  moisture.  The  dry 
faecal  matter  passed  daily  is  therefore 
about  1  oz.  per  adult  head  of  the  popu- 
lation. Of  this  dry  faecal  matter,  about 
88  per  cent,  is  organic  matter  (of  which 
6  parts  are  nitrogen)  and  12  per  cent,  in- 
organic, of  which  4  parts  are  phosphoric 
acid.  Of  this  dry  faecal  matter  11  per 
cent,  is  soluble  in  water. 

Taking  a  population  of  10,000  adults, 
it  follows  that  the  moist  faecal  matter 
passed  daily  is  equal  to  2,500  Ibs.  (=1 
ton,  2  cwt.,  8  Ibs.)  or  1.116  ton,  whilst 
the  dry  faecal  matter  is  equal  to  625  Ibs. 
(5  cwtl,  2  qrs.,  9  Ibs.). 


The  facts,  therefore,  respecting  the  ex- 
creta of  a  population  of  10,000  adults 
may  be  thus  tabulated  : 

TABLE    I. — F^CAL    MATTER    PASSED    PER 
10,000  OF  ADULT  POPULATION  PER  DIEM. 

Pounds. 

Moist  faecal  matter  excreted 2,500 

Dry        "          "  "         (calculating 

75  per  cent,  as  moisture) 625 

Soluble  in  water=68.55  Ibs |  _ 

Insoluble  in  water=556.45  Ibs. . . .  j"  = 

TABLE  II. — URINE  AND  FAECES  PASSED  PER 
DAY  BY  10,000  ADULTS. 


Total 

Solids 

Solids 

Solids 

Water. 

insol- 

solids. 

dry. 

soluble. 

uble. 

Moist 
Ibs. 

Gallons. 

Ibs. 

Ibs. 

Ibs. 

Faeces 

2500 

187.5 

625.0 

68.55 

556.45 

Urine. 

— 

3750.0 

1581.21 

1581.21 

— 

3937.5 

2206.21 

1649.76 

556.45 

The  following  table  has  been  adapted 
from  Letheby.  The  quantities  given  are 
somewhat  below  the  normal.  The  facts 


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Constituents. 

UBINE. 
e  
tuents  
lie  matter  
ning  nitrogen  
al  matter  — 
ning  phosphoric  acid, 
potash  

FAECES. 

es  
Ltuents  
vie  matter  
ning  nitrogen  
al  matter  
ning  phosphoric  acid, 
potash  

iff 

lull? 

were  collected  from  a  Dumber  of  sources, 
the  ratio  of  children  to  adults  being  that 
adopted  by  Boderer  and  Eichhorn. 

My  own  experiments  would  lead  me  to 
give  one  pint  as  an  average  quantity  of 
urine  passed  by  children  daily  up  to  the 
age  of  ten  years,  the  quantity  gradually 
increasing  up  to  three  pints  in  the  adult. 
The  solid  constituents  of  the  urine  which, 
at  the  age  of  ten,  are  on  an  average  0.8 
oz.  daily,  increase,  according  to  my  ob- 
servation, up  to  2.5  ozs.  in  the  adult. 
The  quantity  passed  by  girls  and  women 
is  rather  less  than  that  passed  by  boys 
and  men. 

The  faeces  passed  by  girls  and  women 
are  considerably  less  than  that  passed  by 
boys  and  men.  The  calculations  in  the 
table  state  the  amount  as  less  than  one- 
third.  My  own  observations,  however, 
scarcely  support  these  numbers.  It  would, 
I  think,  be  more  accurate  to  regard  the 
faecal  matters  passed  by  female  children 
and  adults  as  about  one  half  that  passed 
by  male  children  and  adults. 


8 

VALUE  OF  NIGHT  SOIL  (HUMAN  EXCRETA). 

Urine,  in  its  natural  condition,  has  a 
theoretical  value  of  between  15s.  and  16s. 
per  ton.  The  dry  solid  matters  of  the 
urine  have  a  theoretical  value  of  about 
£18  16s.  per  ton. 

The  quantity  of  ammonia  per  year 
voided  by  the  average  individual  in  the 
urine  has  been  stated  as  from  10  Ibs.  to 
11.32  Ibs.,  having  a  value  on  the  lower 
quantity  of  6s.  8d.,  and  on  the  higher  of 
7s.  3d. 

Faecal  matter,  in  its  moist  and  natural 
condition,  has  a  theoretical  value  of  £1 
7s.  6d  per  ton.  The  dry  solid  matters 
of  faeces  have  a  theoretical  value  of  £5 
17s.  7d.  per  ton. 

The  quantity  of  ammonia  voided  per 
year  in  the  faeces,  by  an  average  individual, 
is  estimated  at  1.64  Ibs.,  having  a  value 
of  about  Is.  3d. 

The  estimates  given  above  are  based 
on  the  agricultural  values  of  the  nitrogen 
calculated  as  ammonia,  together  with  the 
phosphoric  acid  and  potassium  salts,  these 
being  materials  of  sparing  occurrence  in 


9 

land,  but  entering  largely  into  the  com- 
position of  every  variety  of  agricultural 
produce.  Lime,  magnesia,  and  iron, 
equally  essential  to  plant  development, 
occur  largely  in  most  soils.  The  details 
are  stated  in  the  second  table. 

Respecting  the  value  of  the  nitrogen, 
however,  of  sewage,  Voelcker  regards 
it  as  at  least  of  10  per  cent,  less  value 
than  the  nitrogen  of  ammoniacal  salts 
ready  formed. 

Authorities  differ  between  6s.  6d.  and 
£1  in  estimating  the  annual  value  of  the 
excreta  of  one  adult.  Thudichum  gives 
it  at  £1;  Hofmann  and  Witt  at  11s.  9|d.; 
Voelcker  at  9s. ;  Lawes  and  Way  at  8s. 
5|d. ;  Anderson,  of  Glasgow,  at  8s. 

In  the  table  we  have  estimated  the 
mixed  excreta  of  the  population  as  worth 
15s.  8d.  per  ton  in  their  natural  condition, 
and  the  solid  matter  of  such  mixed  ex- 
creta as  worth  £14  16s.  4d.  per  ton. 

In  this  table,  moreover,  no  corrections 
are  made  in  stating  the  value  of  the  solid 
constituents,  either  for  the  loss  of  am- 
monia that  would  occur  during  evapora- 


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11 

tion,  or  for  the  soluble  phosphoric  acid 
of  the  fresh  excreta  becoming  insoluble 
by  its  combination  with  lime,  after  dry- 
ing. No  doubt  the  loss  from  these  causes 
is  considerable,  and  tend  to  show  that, 
when  used  as  a  manurial  agent,  sewage 
should  be  applied  to  the  land  in  its  fresh 
state. 

•  These  estimations  of  value  are  theoret- 
ical only.  Cesspool  matter  in  Paris  fetch- 
es from  1  franc  to  1  franc  25  cents  per 
cube  meter  (about  1  ton),  whilst  in  Hol- 
land and  Belgium  the  average  is  one  shil- 
ling per  head  per  annum  for  the  excreta. 
It  would  scarcely  be  an  exaggeration  to 
place  the  real  value  of  the  excreta  at 
about  one- sixth  their  calculated  value. 

Certain  comparisons,  in  respect  of  fer- 
tilizing power  (and,  therefore,  of  agricul- 
tural value),  are  worth  noting : 

1  Ib.  of  human  excrement =13  Ibs.  horse  dung. 

1  Ib.  of  human  excrement 

=6  Ibs.  of  cow  dung  (Macaire  and  Marcet). 

Excreta  of  one  adult  (solid  and  liquid) 

= Droppings  from  one  sheep  (Mechi). 


12 


Yearly  excreta  (solid  and  liquid)  of  one  adult 
—75  Ibs.  of  Peruvian  guano  (Voelck- 
er).     (This  will  yield  3.2  bushels 
of  grain.) 

Yearly  excreta  (solid  and  liquid)  of  one  adult 
==  Yield  of  sufficient  nitrogen  (16.41 
Ibs.)  to  furnish  the  nitrogen  of 
800  Ibs.  of  wheat,  rye,  or  oats  ;  or 
900  Ibs.  of  barley,  value  £5. 
(Boussingault. ) 

MIDDENS. 

Sewage  absorbents. — The  cesspool  and 
the  midden  were  the  first  attempts  at  col- 
lecting excreta,  not  so  much,  however, 
for  the  purpose  of  profit  as  with  the  idea 
of  preventing  nuisance.  The  cesspool 
had  many  and  great  disadvantages,  not 
the-  least  of  which  were  the  noxious  in- 
halations evolved,  the  necessity  for  occa- 
sional emptying,  and  the  pollution  of  the 
drinking  water  of  the  wells  in  the  neigh- 
borhood. The  ash  pit  midden  had,  and 
has,  its  advantages  and  its  difficulties. 
Of  the  difficulties,  the  education  of  the 
people  to  use  them  properly  was  chief,  a 
difficulty,  however,  that  applies  almost  as 
much  to  water  closets  as  to  middens.  A 


13 


second  difficulty  in  the  use  of  the  middens 
consisted  in  securing  proper  scavenger- 
ing  arrangements  by  the  local  authority/a 
difficulty,  it  may  be  again  noted,  not  one 
iota  less  great  in  securing  the  efficient 
treatment  of  sewage.  Provided  the  mid- 
den be  regularly  attended  to  and  proper- 
ly constructed,  e.  g.,  erected  away  from 
the  house — the  pit  small — roofed  in  so 
as  effectually  to  stop  out  rain  or  other 
water— floored  with  sloping  flags  to  ren- 
der the  removal  of  the  contents  easy — 
impervious  to  surface  water  and  not 
drained,  dryness  of  contents  being 
effected  by  the  use  of  ashes  well  distrib- 
uted over  the  soil — there  are  more  ob- 
jectional  ways  of  dealing  with  refuse 
than  by  the  midden  system.  Under  con- 
ditions of  individual  and  general  super- 
vision, the  compost,  if  sufficiently  often 
removed,  need  not  be  a  nuisance.  But  if 
the  midden  be  neglected  by  the  public 
authority  and  by  the  householder,  no 
doubt  it  may  become  a  prolific  source  of 
disease,  as  Manchester  and  Liverpool 
can  testify. 


14 


The  advantages  of  the  pail  system  are 
not  to  be  overlooked.  Thus  the  pails  are 
always  placed  outside  the  house  ;  whilst 
a  certain  regular  process  of  inspection  is 
rendered  necessary,  ensuring  the  detec- 
tion of  a  nuisance  before  it  becomes  a 
source  of  danger.  In  time  of  epidemics, 
again,  disinfectants  may  be  extensively 
used  in  the  pails  as  they  are  being  dis- 
tributed. 

Another  great  advantage  of  the  mid- 
den  system  is  to  be  found  in  the  diver- 
sion of  excremental  matters  from  rivers 
and  watercourses.  Much  sewage  at  Man- 
chester is  thus  kept  out  of  the  River  Med- 
lock.  Strange  to  say,  however,  the  Riv- 
ers Pollution  Commissioners  (Dr.  Frank- 
land)  state  that  the  sewage  from  water 
closet  towns  is  no  worse  than  that  from 
midden  towns.  The  following  is  an  ab- 
stract of  the  results  recorded  by  Dr. 
Frankland : 


15 

AVERAGE  RESULTS. 

Matters  in  Solution. 

Total    Chlo-Total  Nit-' 
Solids,    rine.       rogen. 

Midden  town  sewage  (37)  ^7  AQ      ft  ftQ      A  *o 
samples  from  15  towns);57'68  '  8'08  '  4'53 

Matters  in 
Suspension. 

Total.         Organic. 

Midden  town  sewage  (37  )       <vr  QQ  u.  01 

samples  from  15  towns)  f       27'3S 

Matters  in  Solution. 

Total    Chlo-Total  Mt> 
Solids,      rine.     rogen. 
Water  closet  town  .sew-) 
age  (50  samples  from  17  >  50. 54  .  7.46  .  5.41 
towns) ) 

Matters  in 
Suspension. 

Total.         Organic. 
Water  closet  town  sew-) 

age   (50   samples  from-       31.29     ..     14.36 
17  towns ) 

On  this,,  one  question  suggests  itself — 
how  is  it  that  the  suspended  matter  in 
the  sewage  of  midden  towns  is  almost 
identical  with  that  from  water  closet 
towns,  seeing  that  Dr.  Frankland  states 
that  an  average  of  25,561  tons  of  solid 
matter  per  annum  is  annually  kept  out  of 
the  sewers  at  the  several  midden  towns 
mentioned. 


16 

The  pail  system  may  consist  either  in 
the  use  of  a  little  disinfectant  or  of  some 
absorbent  material. 

Adopting  Mr.  Gilbert  R.  Redgrave's 
classification  of  the  pan,  pail  and  midden 
systems  of  disposing  of  sewage,  we  shall 
discuss  the  subject  under  the  following 
three  heads : — I.  Pails  without  absorb- 
ents. II.  Pails  with  absorbents.  III. 
Pails  used  for  the  joint  collection  of  ashes 
and  excreta. 


I.  PAILS  WITHOUT  ABSOKBENTS. 

Of  these  the  Rochdale  system  may  be 
regarded  as  principal.  In  support  of  the 
non-use  of  any  absorbent,  it  is  urged 
that  to  keep  out  "  the  profligate  as- 
sociate" is  a  main  object;  concentration, 
not  increase  of  bulk,  being  the  point  to 
be  aimed  at.  The  execreta  and  dry  house 
refuse  should  be  collected  at  intervals  in 
separate  tubs  of  special  construction,  the 
excreta  tub  being  fitted  with  an  air-tight 
lid,  so  that  transport  may  be  effected 
without  causing  a  nuisance.  The  cost 


17 


per  pail  per  annum  is  about  5s.  8d.     The 
ashes  are  carefully  screened  and  sorted. 

From  the  experience  •  of  many  towns 
(Rochdale,  Salford,  etc.)  it  would  appear 
that  two  men  and  one  horse  (say  at  a 
working  cost  of  £3  per  week)  can  remove 
600  tubs  or  pails  per  week,  each  pail  con- 
taining an  average  of  84  Ibs.  of  excre- 
mental  matter.  This  equals  22-J-  tons  per 
week  at  a  working  cost  of  2s.  9d.  per  ton. 
At  Rochdale  10,112  pails  were  in  use  in 
1882,  the  weight  of  excreta  collected  be- 
ing 8,518  tons  and  of  refuse  ashes  18,396 
tons,  from  15,289  houses  and  237  rnilJs 
and  workshops,  with  an  estimated  popu- 
lation of  65,500.  In  1881,  552  tons  of 
manure  was  manufactured.  It  is  calcu- 
lated that  each  tub  is  used  by  9.2  per- 
sons living  in  2.2  houses,  the  yield  being 
2.07  cwts.  of  excreta  per  head  per  annum. 
At  Halifax  it  was  calculated  that  each 
tub  is  used  by  10.9  persons  living  in  2.6 
houses,  the  yield  being  3.26  cwt.  of  ex- 
creta per  head  per  annum.  At  Birming- 
ham the  returns  give  from  9.6  to  11.5  Ibs. 
per  week  per  head. 


18 


II.  PAILS  WITH  ABSORBENTS. 
In  many  places  the  use  of  boxes,  pails, 
or  tubs,  charged  with  various  absorbent 
materials  (ashes,  etc.)  has  been  adopted. 
Numerous  substances  have  been  suggest- 
ed as  absorbents.  Of  these  Liebig  re- 
commended coarsely  powdered  bog  turf, 
and  Stanford  charred  seaweed  Stanford 
claims  that  seaweed  is  three  times,  weight 
for  weight,  as  effective  as  dry  earth  (1 
cwt.  being  sufficient  for  one  month  for  a 
closet  daily  used  by  six  persons).  He 
claims,  moreover,  that  it  is  easily  reburnt, 
and  that  the  ammonia  and  fixed  salts 
have  been  recovered,  the  charcoal  remains 
as  effective  as  before.  Various  forms  of 
refuse  too  have  been  suggested  as  ab- 
sorbents, of  which  may  be  noted,  refuse 
wool  or  shoddy,  dry  horse  dung,  spent 
dye  stuffs,  etc.  At  certain  towns  spent 
dye  wood  (such  as  fustic),  in  the  manner 
suggested  by  Goux,  viz.,  ramming  into  a 
tub  by  a  central  core,  so  as  to  give  a  uni- 
form lining  to  the  tub,  has  been  employed. 
Thus  splashing  is  prevented.  This  method 
necessitates  the  frequent  removal  of  the 


19 


excreta  (otherwise  the  absorbent  lining 
would  break  down  and  a  semi-liquid  mass 
result),  and  it  is  also  necessary  that  the  re- 
ceptacle should  be  tightly  secured  before 
removal,  to  prevent  escape  of  offensive 
effluvia  during  transit. 

III.  PAILS  USED  FOR  THE   JOINT  COLLEC- 
TION OF  ASHES    AND  EXCRETA. 

Of  this  method  the  system  adopted  at 
Nottingham  is  a  case  in  point.  Here  the 
tub  takes  the  place  of  the  midden  pit.  It 
is  to  be  noted  that  the  ashes  are  of  less 
quantity  in  summertime,  when  the  chance 
of  nuisance  is  greatest. 

With  respect  to  the  mechanical  appli- 
ances suggested  for  sifting  the  ashes,  so 
as  to  apply  only  the  smaller  breeze  to  the 
excreta,  practice  proves  them  somewhat 
unsuccessful. 

The  compost  is  removed  every  two  or 
three  months  and  conveyed  to  the  manure 
wharf,  where  it  is  emptied  into  barges  and 
sold  at  a  price  that  covers  two-thirds  of 
the  cost  of  scavenging. 


20 


At  Birmingham,  where  galvanized  pails 
are  used  to  the  extent  of  some  40,000 
(representing  a  population  of  250,000), 
the  contents  are  collected  weekly.  These 
are  emplied  into  a  vat  at  the  place  of  de- 
posit, and  some  sulphuric  acid  added  to 
fix  the  ammonia.  The  contents  are 
passed  into  a  drying  machine,  consist- 
ing of  a  steam  jacketed  cylinder  with- 
in which  are  revolving  arms,  the  neces- 
sary heat  being  obtained  by  burning  the 
cylinders  and  garbage  collected  in  the 
town.  The  clinkers  are  utilized  for  vari- 
ous purposes. 

The  process  adopted  at  Manchester, 
devised  by  Mr.  Leigh  and  carried  out  by 
Mr.  Whiley,  was  described  in  detail  by 
Mr.  Alliott,  of  Nottingham,  at  the  Society 
of  Arts  Conference,  1877.  The  objects 
are  (1)  the  disinfection  of  the  pail  con- 
tents by  the  use  of  charcoal,  produced  by 
charring  street  sweepings  •.  and  (2)  the 
reduction  in  bulk  of  the  matters  so  col- 
lected. For  the  purpose  of  reducing 
bulk  the  liquid  in  the  pails  is  drained  off, 
and  concentrated  by  a  low  heat  to  the  con- 


21 


sistency  of  treacle  (about  one-tenth  the 
original  bulk.) 

I  do  not  propose  discussing  the  pneu- 
matic system  of  collecting  excreta.  In 
certain  places  on  the  Continent  (Paris, 
Milan,  &c.),  the  sewage  is  collected  in 
water-tight  cesspools.  These  are  emptied 
by  atmospheric  pressure,  the  contents 
being  forced  into  movable  exhausted 
iron  tanks,  through  flexible  tubes  lowered 
into  the  cesspool  for  the  purpose.  By 
this  means  the  escape  of  noxious  effluvia 
is  supposed  to  be  prevented. 

The  cost  of  removing  the  excreta  at 
Paris  is  about  £5  per  house  per  annum. 
The  material  is  converted  at  Yillette  in- 
to poudrette,  great  nuisance  resulting. 
The  arrangements  of  Liernur  (which  have 
been  adopted  in  Amsterdam,  and  to  a  cer- 
tain extent  in  Prague),  are,  in  many  re- 
spects, similar.  Liernur  suggests  cess- 
pool tanks  being  placed  in  the  middle  of 
a  street,  each  tank  communicating  with 
from  fifteen  to  twenty  houses. 

The  systems  of  Berlier,  partly  in  use 
in  Paris  since  1881,  and  of  Shone,  a 


22 


method  of  pumping  sewage  by  small 
pneumatic  pumping  engines,  the  power 
being  generated  at  a  central  station,  need 
only  be  mentioned. 

As  general  rules  we  consider  : 

1.  That    the    removal    of    the   pails 
should  be  under  the  control  of  the  local 
authority. 

2.  That  on  an  average  they  should  be 
renewed    once    a    week,    a    clean,    well- 
washed   pail  being   substituted  for   the 
full  one. 

3.  That  air- tight  covers  should  be  fit- 
ted to  the  pails  before  removal,  and  that 
they  should  be  conveyed  in  air-tight  vans 
to  the  depot. 

The  utilization  of  the  excreta  collected 
in  pails  is  a  matter  of  great  difficulty.  At 
best  a  low  class  of  manure  results,  unless 
some  form  of  concentration  be  adopted. 

Voelcker  states  that  having  examined 
every  form  of  night-soil  manure,  he  never 
found  one  having  a  theoretical  value 
greater  than  £1  per  ton,  unless  the 
manure  had  been  specially  fortified  with 
guano,  or  superphosphate,  or  sulphate  of 


23 

ammonia,  etc.  The  better  varieties  he 
valued  at  from  15s.  to  17s.  6d.  per  ton, 
whilst  those  less  carefully  prepared  were 
not  worth  more  than  from  7s.  6d.  to  12s. 
6d. 

THE  EARTH  CLOSET. 

The  disinfecting  power  of  earth  has 
been  known  from  remote  antiquity.  In 
China,  the  formation  of  a  manure  by  mix- 
ing earth  with  the  excreta  is  of  ancient 
date. 

In  this  country  Kosser  in  1837  pro- 
posed the  admixture  of  urine  and  faecal 
matter  with  earth,  lime,  etc.  The  sug- 
gestion took  no  practical  shape  until 
1858,  when  the  Kev.  Henry  Moule,  the 
vicar  of  Fordington,  investigated  the  dis- 
infecting and  deodorizing  power  of  earth 
on  privy  soil.  As  the  result  he  invented 
his  earth  closet.  At  his  own  vicarage, 
where  the  cesspool  proved  to  be  danger- 
ously near  the  well,  he  abolished  the  cess- 
pool, and  placed  buckets  beneath  the  pans. 
Their  contents  were,  in  the  first  instance, 
mixed  with  dry  sifted  earth,  earth  after- 


24 


wards  being  placed  in  the  bucket  itself,  and 
the  compost  left  to  consolidate  in  a  shed. 
After  five  or  six  weeks  he  found  that  the 
material  had  entirely  lost  its  offensive 
odor,  and  was  sufficiently  dry  to  be  used 
again.  Thus  eventually  he  not  only  dis- 
infected his  sewage,  but  produced  a  ma- 
nure containing  one- third  its  weight  of 
dry  excrement.  The  next  point  was  the 
mere  mechanical  construction  of  a  closet, 
worked  by  a  handle,  with  contrivances  to 
secure  the  application  of  a  proper  pro- 
portion of  dry  earth.  The  earth  may, 
however,  be  thrown  into  the  closet  in  one 
application  daily,  a  method  adopted  in 
the  latrines  at  Lancaster,  which  are  under 
the  control  of  the  local  authority. 

As  regards  the  earth  best  adapted  for 
the  purpose,  a  well-dried  clayey  earth, 
that  is,  a  heavy  soil  loaded  with  clay,  holds 
the  first  place ;  peaty  earth  comes  next, 
although  for  efficiency  a  long  way  behind 
a  clayey  earth.  The  peaty  earth  used  at 
the  Wimbledon  Camp  in  1867  was  not 
satisfactory,  as  it  produced  a  wet  and 
sour  compost.  Sand  and  clay  are  found 


25 


to  have  very  little  deodorizing  power, 
and  are  therefore  ill  suited  for  the  earth 
closet.  The  clay  soil  must  be  well  dried 
artificially  (for  in  a  damp  condition  its 
absorbent  power  is  inferior),  and  after 
drying,  powdered  and  sifted. 

About  4£  Ibs.  of  dry  earth  per  head 
per  day  (i.e.,  1^  Ibs.  for  each  visit,  three 
visits  being  allowed  for  each  person)  is 
required  to  obtain  a  consolidated  and  un- 
offensive  compost.  This  quantity  was 
ultimately  used  at  the  Dorset  County 
Jail,  the  3  Ibs.  per  head  of  earth,  used 
in  the  first  instance,  being  found  insuf- 
ficient. A  village  of  1,000  persons  would 
need,  therefore,  about  2  tons  of  dry  earth 
per  day.  The  dry  earth  system  was  used 
at  the  Dorset  County  School,  at  the  vil- 
lages of  Halton  and  Aston  Clinton  near 
Windover,  in  Lancaster,  and  at  the  Wim- 
bledon Camp.  In  this  latter  case  Dr. 
Buchanan  closely  investigated  the  work- 
ing of  the  process. 

After  the  removal  of  the  earth  it  may 
be  dried  and  returned  to  the  closet  until 
its  manurial  value  justifies  its  sale. 


26 


As  regards  composition  and  value  of 
the  product,  much  will  depend  on  the 
demand,  and  on  the  method  adopted  in 
working  (i.e.,  how  many  times  the  mate- 
rial had  been  used).  At  Lancaster  the 
compost  fetched  7s.  6d.  to  10s.  per  cubic 
yard.  At  Dorset  County  Jail  it  reached 
£1  per  ton,  and  at  the  Dorset  County 
School  £2  to  £3  per  ton.  Perhaps  10s. 
per  head  of  the  population  annually  might 
be  taken  as  an  approximate  value. 

The  dry  earth  system  has  certain  defi- 
nite advantages  over  the  water  closet. 
The  first  cost  is  less.  It  reduces  the 
quantity  of  water  required  by  each  house- 
hold. The  closet  is  less  liable  to  go 
wrong,  to  suffer  injury  from  frost,  or  to 
be  damaged  by  improper  substances  be- 
ing thrown  into  it.  No  doubt  an  intelli- 
gent person  can  manage  it,  but  if  it  be 
used  in  villages  it  should  be  managed  by 
the  local  authority,  easy  access  to  the 
closets  by  the  scavengers  being  in  such 
case  indispensable.  Of  course  a  dry  earth 
system  does  not  supersede  the  necessity 


27 


for  some  independent  means  of  removing 
slops,  rain,  and  subsoil  water. 

A  still  further  advantage  claimed  for 
the  earth  closet  is  the  manurial  value  of 
the  compost,  and  the  ease  with  which  it 
may  be  stored  until  required. 

No  doubt  the  earth  closet  has  its  ob- 
jections. Of  these  a  certain  filthiness 
(real  or  imaginary),  and  the  difficulties  of 
supplying  the  necessary  quantity  of  dry 
earth  and  of  removing  the  compost,  are 
those  chiefly  urged.  No  doubt  the  col- 
lection of  material  that  may  be  more  or 
less  foul  as  the  closet  has  or  has  not  been 
attended  to  by  the  scavengers,  and  the 
after  distribution  of  the  compost,  com- 
pare, at  first  thought,  unfavorably  with 
the  cleanliness  of  water,  and  the  ease 
with  which  it  serves  to  convey  the  filth 
from  the  closet  to  the  field.  But  this  as- 
sumes (1st)  no  misadventure  of  the  water- 
carried  sewage  between  closet  and  field  ; 
(2d)  a  farm  and  a  crop  ready  at  all  times 
and  seasons — wet  or  dry,  summer  or 
winter — to  receive  and  to  appropriate  it; 
and  (3d)  no  escape  of  noxious  effluvia 


28 


and  miasms,  no  spread  of  disease,  and 
no  pollution  of  water  courses.  How  far 
such  assumptions  are  realized,  I  shall 
consider  presently. 

Earth  closets  have  been  largely  used, 
and  their  use  is  rapidly  extending,  in  In- 
dia, where  the  drying  of  the  earth  is  a 
comparatively  easy  process.  The  author- 
ities in  India,  in  1867,  reported  to  the 
Secretary  of  State  that  Moule's  system, 
which  was  then  generally  employed  in 
the  barracks,  jails,  hospitals,  and  public 
institutions  of  the  three  presidencies,  had 
been  found  to  be  a  great  public  benefit. 
I  can,  myself,  bear  testimony  to  the  ex- 
cellent results  of  the  dry  earth  system 
where  the  closets  are  properly  attended 
to — proper  earth  used — and  the  materials 
properly  dried. 

SEWAGE. 

We  now  turn  to  water-carried  sewage 
— its  composition,  value  and  treatment. 

By  the  phrase  "  the  sewage  of  a  town" 
is  implied : 

(1.)  The  excreta  (solid  and  liquid)  of 
the  population. 


29 


(2.)  The  refuse  from  kitchens,  Sun- 
dries, etc. 

(3.)  The  drainings  from  stables,  slaugh- 
ter-houses, etc. 

(4.)  The  liquid  impurities  resulting 
from  various  trade  operations  (brewer- 
ies, dyehouses,  fellmongeries,  etc.) 

(5.)  The  washings  of  public  thorough- 
fares, etc. 

(6.)  Domestic  and  subsoil  water. 

To  speak  broadly,  we  may  define  sew- 
age as  u  the  refuse  of  communities— their 
habitations,  streets  and  factories." 

It  is  manifest,  therefore,  that  it  is  not 
possible  to  define  broadly  what  consti- 
tutes "  average  sewage."  The  quantity 
and  quality  of  the  sewage  of  a  town  will 
be  influenced  by  the  following  amongst 
other  conditions: 

(1.)  The  number  and  nature  of  the 
manufactures  and  trade  operations  pecu- 
liar to  the  place,  and  which  are  drained 
into  the  sewers. 

(2.)  The  existence  of  an  excessive 
number  of  stables  (such  as  result  from 
the  presence  of  barracks). 


30 


(3.)  The  volume  of  water  supplied  to 
the  inhabitants. 

(4.)  The  proportion  of  rain  or  surface 
water  admitted  into  the  sewers. 

(5.)  The  quantity  of  subsoil  water  that 
leaks  into  the  sewers. 

(6.)  The  density  and  general  habits  of 
the  people. 

(7.)  The  season  of  the  year. 

(8.)  The  time  of  day. 

Sewage  may  be  subdivided  into — 

1.  Domestic  sewage. 

2.  Manufacturing  refuse. 

3.  Bain  and  storm  water. 

We  shall  find,  when  we  come  to  discuss 
the  treatment  of  sewage,  the  first  great 
difficulty  is  the  large  quantity  to  be  dealt 
with.  It  has  been  suggested  to  meet 
this  difficulty  of  quantity  by  adopting  a 
duplicate  set  of  sewers,  the  one  for  sew- 
age proper  (domestic  and  manufacturing), 
and  the  other  for  storm  and  rain  water, 
or  at  any  rate  for  the  larger  part  of  the 
rain  water.  For  irrigation  purposes,  no 


31 


doubt,  it  is  desirable  to  have  the  domes- 
tic sewage  as  little  diluted  as  possible^ 
but  for  chemical  treatment  dilution  within 
certain  limits  is  not  an  evil.  A  separate 
system  must  be  more  expensive,  besides 
which  it  robs  the  sewers  of  one  means 
of  natural  and  effective  flushing,  such  as 
occurs  after  heavy  rains.  It  also  excludes 
from  the  sewage  to  be  treated  many  ma- 
terials (e.g.,  road  washings),  that  certainly 
need  treatment  as  much  as,  if  not  more 
than,  any  sewage  proper.  To  limit  the 
water  for  removal  of  filth  to  its  smallest 
quantity  is  a  sound  principle,  but  there 
is  a  danger  in  over-reduction.  The  most 
earnest  advocates  of  the  separate  system 
scarcely  see  their  way  to  exclude  from 
the  public  sewers  the  rain  falling  on  pri- 
vate property,  as  this  would  for  the  most 
part  necessitate  two  sets  of  house  drains. 
It  may  be  admitted  that  both  the  separ- 
ate and  combined  systems  have  their 
merits  and  defects,  and  that  certain  local 
conditions  may  determine  the  choice  of 
the  system. 


32 


The  arguments  used  in  favor  of  a  sep- 
arate system  are : 

(1.)  Greater  uniformity  in  the  quantity 
of  sewage  conveyed. 

(2.)  The  prevention  of  deposits,  the  di- 
mensions of  the  pipes  being  capable  of 
more  accurate  adjustment,  permitting 
them  to  be  daily  filled  to  their  maximum 
at  the  hour  of  maximum  flow. 

(3.)  If  the  sewage  has  to  be  pumped, 
expense  will  be  saved  by  the  limitation 
of  quantity. 

(4.)  Prevention  of  floodings  from  the 
capacity  of  the  sewers  being  overtaxed, 
or  from  obstruction  taking  place  in  the 
surface  channels  during  times  of  heavy 
rain,  or  on  the  occurrence  of  a  rapid 
thaw  after  a  long  period  of  snow.  Dan- 
ger arising  from  the  gases  in  the  sewers 
being  forced  by  the  rush  of  water  thus 
filling  the  sewer,  being  driven  through 
the  nearest  outlet,  and  possibly  through 
house  connections,  will  be  avoided. 

(5.)  Prevention  of  precipitation,  and 
so  of  deposit  in  the  sewers,  from  earthy 
matter  (such  as  building  lime)  being  car- 


33 


ried  in  at  storm  time,  together  with  road 
detritus,  leaves,  etc.,  and  which,  under 
ordinary  conditions,  might  not  be  removed 
until  the  next  heavy  rain. 

(6.)  If  obstruction  occurs,  a  compara- 
tively small  volume  of  water  will  be  suf- 
ficient to  flush  the  sewers  effectively  on 
account  of  the  relative  smallness  of  pipe. 

(7.)  That  with  small  pipes,  good  venti- 
lation of  the  sewers  may  be  more  easily 
effected. 

(8.)  That  the  nuisance  arising  from  or- 
ganic matters  being  carried  into  the  pipes 
at  the  time  of  storm,  and  putrefying  on 
the  upper  portions  of  the  sewer  pipe, 
where,  under  normal  conditions  of  flow, 
it  forms  a  slimy  coating  and  develops 
swarms  of  organisms,  will  be  prevented, 
the  sewers  being  filled  daily  to  their  max- 
imum working  capacity. 

(9.)  That  the  quantity  of  sewage  to  be 
dealt  with  would  be  greatly  decreased. 

On  the  other  side  it  is  urged  that, 
however  sound  it  may  appear  in  theory 
to  urge  "the  rainfall  to  the  river,  the 


34 


'  sewage  to  the  soil,"  there  are  manifest 
objections  to  the  separate  system : 

1.  That  it  is  practically  impossible  thus 
to  separate  rain  water  and  sewage,  things 
that  ought  not  to  be  in  the  rain  water 
pipes  being  certain  to  get  there. 

2.  That  the  road  washings  and  rilth, 
making  the  first  wash  of  a  heavy  storm, 
is  most  often  far  more  filthy  than  the 
very  worst  sewage,  and,  therefore  special- 
ly requires  treatment. 

3.  That  storm  water  is  the  natural  flush 
water  for  the  sewers. 

It  may  be  said  that  the  third  objection 
may  be  met  by  automatic  flush  tanks  ; 
the  second,  by  effective  scavenging ;  the 
first  by  educating  the  people.  We  have 
not  yet  attained  the  ideal  of  sanitary 
work.  A  separate  system  would,  I  fear, 
mean  the  intermittent  pollution  of  our 
water-courses.  There  are  legal  difficul- 
ties, too,  in  carrying  it  out,  which  I  will 
not  discuss. 

I  do  not  deal  with  the  question  of  cost, 
except  to  say  that  the  mere  size  of  pipe 
is  not  the  only,  nor  is  it  the  main  ques- 


35 


tion  to  be  considered  in  laying  pipes,  the 
excavation,  paving,  etc.,  being  practically 
the  same,  whether  pipes  be  large  or 
small. 

COMPOSITION  OF  SEWAGE. 

Sewage,  we  have  said,  is  a  complex 
fluid ;  no  absolute  average  analysis  can 
therefore  be  stated.  It  will,  however,  be 
a  good  starting  point  to  regard  the  aver- 
age sewage  of  London  as  a  standard,  and 
to  speak  of  sewage  of  greater  polluting 
power  as  a  strong  sewage,  and  of  less 
polluting  power,  as  a  weak  sewage. 

A  large  number  of  samples  of  London 
sewage  were  examined  by  Dr.  Frankland 
and  myself  between  1883  and  1884.  The 
following  are  certain  average  details 
worthy  of  record.  The  results  are  stated 
in  grains  per  gallon  of  70,000  grains : 

Maximum.  Minimum.    Average. 

Matters  in  solution ...  49 . 77    28 . 42    45 . 213 
Matters  in  suspension.  163 .9      21 . 4      48 . 65 

Ammonia 6.527    2.515    3.012 

Chlorine 8.33      5.67      7.21 

Organic  carbon 3 . 847    2.118    3 . 069 

Organic  nitrogen 2 . 676    0 . 964    1 . 738 

Average  ratio  of  N  to  C  —  1 :  1.77. 


36 


These  results,  however,  take  no  note 
of  true  storm  sewage. 

Whilst  an  assistant  of  Dr.  Letheby,  I 
made,  jointly  with  him,  a  very  large  series 
of  analyses  of  sewage  from  ten  of  the 
large  city  sewers,  the  rate  of  flow  being, 
on  an  average,  3,500  gallons  per  minute. 
The  following  are  average  details : 


Day 

Sew- 
age. 

Night 
Sew- 
age. 

Storm 
Sew- 
age. 

SOLUBLE  MATTERS 

55.74 

65.09 

70.26 

(«  )  Organic  

15.08 

7.42 

14.75 

Containing  nitrogen. 
(b.  )  Mineral  

5.44 

40.66 

5.19 
57.67 

7.26 
55.71 

Containing  phosphor- 
ic acid  

0.85 

0.69 

1.03 

Containing  potash  .  .  . 

1.21 

1.15 

1.61 

SUSPENDED  MATTERS  .... 
(#.)  Organic  

38.15 
16  11 

13.99 

7.48 

31.88 
17  55 

Containing  nitrogen.  . 
(#.)  Mineral  

0.78 
22  04 

0.29 
6.51 

0.67 
14.33 

Containing  phosphor- 
ic acid  

0.89 

0  64 

0  98 

Containing  potash  .  .  . 

0.08 

0.04 

0.16 

It  may  be  of  importance  to  record  that 
at  the  time  the  samples  were  collected 


for  analysis,  37.5  gallons  (6  cubic  feet) 
was  contributed  per  head  of  the  popula- 
tion. Of  this,  80  per  cent,  was  repre- 
sented by  the  water  supply.  The  follow- 
ing table  exhibits,  therefore,  the  weight 
in  pounds  of  the  chief  constituents fof 
375,000  gallons  of  sewage  (mid-day  sew- 
age being  taken  for  comparison)  fur- 
nished daily  by  10,000  people,  and  its 
subdivision  into  excretal  and  non-excretal 
refuse : 


Constituents  of  375,000 
gallons. 

From 
excreta. 

From  refuse 
other  than 
excreta. 

Total. 

SOLUBLE  MATTERS       .    . 

Ibs. 
957 

Ibs. 
2029 

Ibs. 

2986 

(#.)  Organic  

733 

75 

808 

Containing  nitrogen  . 
(b.  )  Mineral  

200 
224 

1954 

291 
2178 

Containing  phosphor- 
ic acid  

30 

16 

46 

Containing  potash  .  .  . 

34 

,31 

65 

SUSPENDED  MATTERS  
(a.  )  Organic  .  . 

316 
356 

1628 
507 

2044 

863 

Containing  nitrogen  . 
(5)  Mineral    

23 
60 

19 
1121 

42 
1181 

Containing  phosphor- 
ic acid.  ...         .... 
Containing  potash  .  .  . 

21 

8 

27 

48 
8 

38 


Putting  these  results  in  a  few  words, 
we  may  say  every  10,000  persons  in  Lon- 
don contribute,  on  an  average,  375,000 
gallons  of  sewage  daily,  and  that  this  in- 
cludes about  1,671  Ibs.  of  organic  matter, 
containing  333  Ibs.  of  nitrogen,  and  335 
Ibs.  of  mineral  matter,  containing  94  Ibs. 
of  phosphoric  acid  and  69  Ibs.  of  potash. 

Of  course  the  total  quantity*  in  any 
given  town  will  depend  on  a  variety  of 
causes.  It  is  certain  to  be  as  much  as 
the  water  supply,  but  it  may  be  a  great 
deal  more.  In  London,  as  we  have  said, 
it  may  be  taken  that  80  per  cent,  of  the 
sewage  is  represented  by  the  water  sup- 

piy-- 

Hofmann  &  Witt  (1857)  examined  the 
sewage  from  the  Savoy  street  sewer,  an 
average  sample  beiog  obtained  by  the 
admixture  of  samples  taken  hourly  dur- 
ing the  twenty-four  hours.  The  results 
were  as  follows,  stated  in  grains  per  gal- 
lon: 

(a.)  Organic 80.70 

Containing  nitrogen 6.76 

(£.)   Mineral (?) 

Containing  phosphoric  acid    1 . 85 
"       '  potash 1.03 


39 

A  large  number  of  sludge  deposits  (to 
which  no  precipitant  was  added)  have 
been  examined  for  the  purpose  of  deter- 
mining the  ratio  of  organic  nitrogen  to 
organic  carbon.  The  results  are  marked 
by  a  great  want  of  uniformity,  ranging 
from  a  ratio  of  1  to  3.4,  to  a  ratio  of  1 
to  9.1.' 

Major  Scott,  after  a  review  of  a  large 
number  of  analyses,  says  :  "  We  may  as- 
sume that  with  each  [one]  part  of  the 
three  fertilizers,  nitrogen,  phosphoric 
acid,  and  potash,  there  will  be  associated 
in  the  sewage  sludge  of  London  20  parts, 
25  parts,  and  56  parts  respectively,  of 
organic  matter." 

Nitrogen  to  organic  matter 1  :  20 

Phosphoric  acid  to  organic  matter. .  1  :  25 
Potash  to  organic  matter 1  :  56 

It  will  be  impossible  for  us  to  discuss 
the  pollution  from  sources  other  than 
excreta,  which,  together,  make  up  the 
complex  fluid  we  designate  sewage.  With 
respect,  however,  to  stable  drainage,  I 
would  note  that  an  average  horse  excretes 


40 


thirteen  times  as  much  fsecal  matter  by 
weight,  and  about  fifteen  times  as  much 
urine,  as  an  adult  man.  It  may  be  noted 
further,  that  both  horses  and  cows  pro- 
duce by  respiration  about  thirteen  or 
fourteen  times  as  much  carbonic  acid  as 
an  adult  man,  and  as  a  consequence  viti- 
ate the  air  in  the  same  ratio.  (Taking 
1,200  cubic  inches  as  the  quantity  of  CO3 
produced  per  hour  by  a  man,  14,750 
inches  is  produced  by  a  cow  or  horse.) 

There  is,  however,  a  not  unimportant 
consideration  which  occurs  in  consider- 
ing the  character  of  a  town  sewage,  viz., 
the  feeding  of  horses.  The  difficulty  of 
dealing  with  the  stable  refuse  where  the 
horses  have  been  fed  upon  maize,  is  far 
greater  than  where  the  animals  have  been 
fed  on  ordinary  corn.  In  my  own  ex- 
perience as  a  health  officer  I  have  had 
abundant  evidence  of  the  peculiarly  of- 
fensive character  of  the  manure  in  such 
cases. 

In  all  inquiries  respecting  tho  sewage 
of  a  town,  the  nature  and  amount  of  the 
liquid  refuse  from  manufacturing  works 


41 


(if  admitted  into  the  sewers)  needs  most 
careful  consideration.  Of  these  I  may 
specially  mention  brewery  refuse,  the 
waste  being  of  a  singularly  offensive  na- 
ture. To  add  to  the  difficulty,  a  consid- 
erable quantity  of  yeast  is  discharged 
with  the  /waste  liquor,  whilst  the  high 
temperature  of  the  refuse  intensifies  the 
trouble  of  treatment.  The  refuse  from 
certain  dye  works,  etc.,  are  also  difficult 
to  deal  with. 

As  regards  street  washings,  the  follow- 
ing details  may  be  worth  noting :  Granite 
roads  were  found  at  the  time  of  a  heavy 
shower  to  discharge  water  into  the  gul- 
leys  containing  800  grains  of  solid  matter 
per  gallon,  of  which  219  grains  were  in 
solution  and  520  in  suspension.  The 
precise  composition  of  the  washings,  will, 
however,  depend  on  many  conditions, 
such  as  extent  of  traffic,  previous  period 
of  drought,  etc.  The  water  from  wood 
paving,  taken  about  the  same  time  as  the 
above,  was  found  to  contain  50  grains  of 
solid  matter  per  gallon,  of  which  40  was 
in  solution  and  10  in  suspension.  Some 


42 

20  samples  of  road  washings  taken  from 
all  kinds  of  roads,  under  circumstances  as 
nearly  as  possible  similar  to  the  condi- 
tions named  above,  were  mixed  together. 
The  water  contained  280  grains  of  solid 
matter  per  gallon,  of  which  120  were  in 
solution  and  160  in  suspension. 

It  would  be  outside  my  province  to 
discuss  the  engineering  details  of  a  sew- 
age scheme.  Yet  let  me  note  that  sani- 
tary medicine  must  take  cognizance  of 
sewage  in  its  progress  through  a  town. 
There  must  be  sufficient  velocity,  as  well 
as  an  economy  of  scouring  power,  in  or- 
der to  prevent  the  solid  matters  from 
collecting.  The  ventilation  of  the  sewers 
is  again  a  question  of  importance  upon 
which  authorities  differ,  and  no  wonder, 
seeing  how  formidable  are  the  difficulties. 

DISCHARGE  or  CRUDE  SEWAGE  INTO  RIVERS. 

Nothing  is  more  certain  than  that  the 
discharge  of  crude  sewage  into  a  river  is 
unadvisable.  It  is,  in  fact,  a  method  of 
shifting  a  nuisance  from  the  nuisance- 
producer  to  his  immediate  neighbor.  The 


43 

evils  arising  from  such  discharge  depend 
mainly  upon  the  suspended  matter  in  the 
sewage.  This,  first  of  all,  floats  about 
near  the  outfall,  certain  portions  of  the 
organic  matter  combining  with  aluminous 
compounds  from  alluvial  mud  raised  by 
tides  and  steamers.  In  time,  deposition 
takes  place.  In  the  course  of  flow  the 
various  ingredients  are  found  to  deposit 
more  or  less  in  the  order  of  their  specific 
gravity.  The  first  deposits  are  mainly 
mineral,  with  small  quantities  of  organic 
matter  carried  down  at  the  same  time. 
The  later  deposits  are  mostly  finely  di- 
vided organic  matter,  along  with  a  small 
quantity  of  mineral  matter.  Thus  there 
occurs,  as  the  result  of  flow,  a  natural 
sorting  of  the  matters  in  suspension. 

The  organic  imparities  of  the  sewage 
in  this  manner  collect  in  the  bed  of  the 
river  and  ultimately  putrefy.  The  gases 
developed  and  bottled  up  in  time  render 
the  solids  sufficiently  buoyant  to  rise  to 
the  surface,  where  the  gases  of  putrefac- 
tion (sulphur  and  phosphorus  compounds 
for  the  most  part)  are  given  off,  the  solid 


44 


matter  again  sinking  to  undergo  fresh 
putrefactive  changes. 

Thus  the  nuisance  from  the  discharge 
of  sewage  into  the  river  may  be  far  more 
offensive  at  a  short  distance  from  the 
outfall, -than  at  the  outfall  itself.  Fur- 
ther, at  a  point  of  slack  water,  the  nuis- 
ance arising  from  these  solids  in  suspen- 
sion may  be  greatly  aggravated. 

As  regards  the  matters  in  solution, 
provided  the  sewage  be  sufficiently  di- 
luted and  allowed  a  certain  flow,  complete 
purification  will  be  effected  by  oxidation. 
This  fact  is  now-a-days  admitted  by 
nearly  all  chemists,  and  need  not  detain 
us  further.  The  self-purification  of  run- 
ning water  is,  however,  not  to  be  regard- 
ed as  an  argument  in  support  of  allowing 
crude  sewage  to  be  discharged  into  a 
river. 

In  1875,  a  committee  of  the  Local 
Government  Board  was  appointed  to 
make  special  inquiry  into  the  practical 
efficiency  of  the  chief  systems  of  sewage 
disposals  then  in  operation,  and  for 
which  loans  had  been  sanctioned  by  the 


45 


Board.  It  reported  in  1876  (Sewage 
Disposal,  Eeport  of  a  Committee,  1876): — 

"  4.  That  most  rivers  and  streams  are 
polluted  by  a  discharge  into  them  of 
crude  sewage,  which  practice  is  highly 
objectionable." 

"  5.  That,  as  far  as  we  have  been  able 
to  ascertain,  none  of  the  existing  modes 
of  treating  town  sewage  by  deposition 
and  by  chemicals  in  tanks  appear  to  effect 
much  change  beyond  the  separation  of 
the  solids,  and  the  clarification  of  the 
liquid.  That  the  treatment  of  sewage  in 
this  manner,  however,  effects  a  consider- 
able improvement,  and  when  carried  to 
its  greatest  perfection,  may  in  some  cases 
be  accepted." 

U6.  That,  so  far  as  our  examinations 
extend,  none  of  the  manufactured  ma- 
nures made  by  manipulating  town's  re- 
fuse, with  or  without  chemicals,  pay  the 
contingent  costs  of  such  modes  of  treat- 
ment ;  neither  has  any  mode  of  dealing 
separately  with  excreta,  so  as  to  defray 
the  cost  of  collection  and  preparation  by 
a  sale  of  the  manure,  been  brought  under 
our  notice." 


46 

"  7.  That  town  sewage  can  best  and 
most  cheaply  be  disposed  of  and  purified 
by  the  process  of  land  irrigation  for 
agricultural  purposes,  where  local  con- 
ditions are  favorable  to  its  application, 
but  that  the  chemical  value  of  sewage  is 
greatly  reduced  to  the  farmer  by  the  fact 
that  it  must  be  disposed  of  day  by  day 
throughout  the  entire  year,  and  that  its 
volume  is  generally  greatest  when  it  is 
of  the  least  service  to  the  land." 

"  8.  That  land  irrigation  is  not  practi- 
cable in  all  cases ;  and,  therefore,  other 
modes  of  dealing  with  sewage  must  be 
allowed." 

This  being  the  sewage  with  which  we 
have  to  deal,  our  object  is  twofold : — 

(1.)  To  make  use  of  any  valuable  con- 
stituents that  it  may  contain  ;  and 

(2.)  To  purify  it. 

Sanitary  requirements,  however,  de- 
mand that  no  nuisance  should  result  in 
the  course  of  the  operation  of  treatment. 

THE  VALUE  OF  SEWAGE. 
The   basis    on    which    the    theoretical 


47 


calculation  of  the  value  of  sewage  may 
be  determined,  is,  authorities  suggest, 
simplicity  itself. 

It  may  be  conceded  that  the  animal 
excreta  are,  practically,  the  only  constitu- 
ents of  manurial  value. 

Having  determined  the  value  of  the 
excreta  of  a  mixed  population,  it  is  only 
necessary  to  know  (1)  the  population  of 
any  given  town,  and  (2)  the  quantity  of 
sewage  produced  during  the  twenty-four 
hours,  to  estimate  the  manurial  value  of 
the  sewage.  It  may  appear  strange, 
however,  the  question  being  one,  we  are 
told,  of  such  simplicity,  that  authorities 
before  the  Select  Committee  of  the 
House  of  Commons  (1862)  should  have 
stated  it  so  variously  as  from  |d.  to  9d. 
per  ton.  Certain  details  upon  which 
these  money  estimates  were  founded  may 
be  noticed. 

The  Rivers  Pollution  Commissioners, 
who  fix  its  value  at  about  2d.  per  ton, 
say :  "  The  money  value  of  these  con- 
stituents (combined  nitrogen,  phosphoric 
acid  and  salts  of  potash),  dissolved  in 


48 

100  tons  of  average  sewage,  is  about  15s., 
whilst  that  of  the  suspended  matters  is 
about  2s.  That  is  to  say  that  100  tons 
of  average  sewage  are  worth  17s.,  or 
about  2d.  per  ton." 

Hofmann  and  Witt  arrived  at  a  similar 
conclusion.  Six- sevenths,  they  say,  of 
the  valuable  matters  in  sewage  are  in  so- 
lution. Keckon  that  700  tons  of  sewage 
contains  one  ton  of  solid  matter,  having 
a  total  money  value  of  £6  Os.  3d.  (£5  5s. 
for  dissolved  matters,  and  15s.  3d.  for 
suspended  matters),  it  follows  that  the 
one  ton  of  sewage  is  worth  about  2d. 

Lawes  and  Gilbert  arrive  at  a  similar 
conclusion.  Beckoning  the  dry  weather 
sewage  of  London  as  24  gallons  daily  per 
head  (™  40  tons  per  head  per  annum), 
and  the  ammonia  as  10  Ibs.  per  head  per 
annum,  the  money  value  would  be  2d. 
per  ton,  whilst  if  the  ammonia  be  taken  at 
12^  Ibs.  per  head  per  annum,  it  would  be 
2^d.  per  ton. 

Take  it,  says  another  authority  (Mr. 
Bailey  Denton),  that  the  fertilizing  ele- 
ments of  one  person  (worth,  let  us  say, 


49 


8s.  4d.  per  year)  are  diluted  with  61  tons 
of  water  (an  average  quantity  contributed 
by  each  individual  to  the  outflow  from 
towns),  the  value  of  sewage  is  8s.  4d. 
divided  by  61,  or  Ifd.  per  ton. 

Such  are  some  of  the  estimates. 

But  there  were  those  who  desired  to 
be  still  more  precise  in  their  calculations. 
Authorities  who  desired  to  be  cautious 
valued  the  London  sewage,  when  the 
population  was  3,000,000,  at  £1,000,000 
sterling,  that  is  at  the  low  estimate 
(ridiculous  to  many  people)  of  6s.  8d.  as 
the  annual  value  of  each  person's  excreta. 
The  two  chairmen  of  parliamentary  com- 
mittees (Mr.  Brady  and  Lord  Robert 
Montagu),  after  a  long  inquiry,  came  to 
the  conclusion  that  London  sewage  is 
equal  in  manurial  value  to  212,842  tons 
of  Peruvian  guano,  with  a  market  price 
of  £2,890,000.  Hofmann  and  Frankland 
considered  that  1,250  tons  of  London 
sewage  contained  the  fertilizing  matters 
of  one  ton  of  Peruvian  guano,  whilst  a 
very  great  authority  indeed,  one  before 
whom  the  chemical  world  justly  bows  in 


50 

admiration,  would  listen  to  nothing  less 
as  the  annual  value  of  the  metropolitan 
sewage  than  £4,081,430. 

Such  being  the  teachings  of  science  as 
to  the  value  of  sewage,  nothing  was  more 
natural  than  to  urge  upon  authorities  its 
application  to  land.  And  here  let  me  say 
at  once,  that  I  distinguish  between  utili- 
zation of  the  sewage  and  its  purification. 
I  consider  them  together,  but  they  are 
totally  different  questions. 

Science  had  its  story  to  tell.  The 
land  acts,  first,  as  a  mechanical  filter,  and, 
secondly,  as  a  chemical  laboratory.  As 
a  filter,  the  larger  insoluble  particles  are 
arrested  on  its  surface,  whilst  the  smaller 
are  entrapped  a  few  inches  down.  The 
water  is  absorbed,  i.  e.,  each  earth  particle 
becomes  covered  with  a  liquid  coating. 
Now  follows  the  work  of  the  chemical 
laboratory.  The  enormous  surface  of 
liquid  thus  formed  is  favorable  to  coerc- 
ing the  combination  of  oxygen  with  the 
organic  impurities  of  this  subdivided 
sewage  water,  carbonic  acid  and  water 
together  with  nitric  acid,  oxidation  being 


51 

assisted  possibly  by  the  presence  of 
certain  micro -organisms  resulting.  The 
organic  matters  on  the  surface  soon  un- 
dergo slow  burning.  The  nitric  acid  is 
your  plant  feeder. 

The  process  of  slow  burning  is  the 
work  of  oxygen,  whilst  that  of  nitrifica- 
tion, as  the  researches  of  Pasteur  and 
Warrington  have  shown,  is  due  to  the 
combined  work  of  oxygen  and  of  certain 
lower  forms  of  life.  Hence,  to  purify, 
you  need  not  only  a  flow  of  sewage,  but 
a  flow  of  air,  that  is,  constant  movement 
regulated  in  its  order.  As  regards  the 
lower  organisms,  they  may  be  already  in 
the  soil  or  be  provided  by  the  sewage. 
The  purifying  power  of  a  soil,  however, 
is  peculiar  to  itself.  You  cannot  com- 
pletely control  aeration,  although  drain- 
age and  loosening  of  soil  will  promote  it, 
and  an  excess  of  irrigation  stop  it.  In 
fact,  the  soil,  as  a  purifying  agent,  is,  to 
say  the  least,  capricious. 

Purification,  the  action  of  the  soil,  is 
greatly  assisted  by  the  action  of  vegeta- 
tion. In  winter  time,  when  there  is  no 


52 

vegetation,  the  soil  only  must  do  the 
work. 

Enthusiasts  fall  of  faith  were  found  to 
embark  in  private  sewage  farms,  whilst 
local  authorities,  anxious  to  save  the 
rates,  offered  the  sewage  to  farmers  in 
their  neighborhood  for  a  corresponding 
return. 

It  was  not  long,  however,  before  a 
certain  unpleasant  awakening  occurred, 
owing  to  the  farmers  declining  even  to 
accept  the  sewage. 

Reasons  for  this  were  sought.  Was  it 
due,  as  was  suggested,  to  the  ignorance 
of  farmers,  and  their  blind  attachment  to 
old-fashioned  ways?  This  contention 
was  scarcely  feasible,  seeing  how  keenly 
they  appreciate  newly  invented  manures 
(e.  </.,  superphosphate,  alkaline  nitrates, 
etc.),  new  implements,  new  methods  of 
subsoil  drainage,  etc. 

Men  began  to  suspect  one  of  two 
things,  either  that  there  was  (a)  some 
obstacle  to  the  agricultural  use  of  sew- 
age ;  or  (A)  that  its  theoretical  value  was 
very  far  from  being  its  practical  worth. 


53 

But  other  facts  than  those  adduced  by 
the  mere  working  farmer,  presented 
themselves  in  the  failure  of  the  farming 
attempts  of  enthusiastic  irrigationists. 
Despite  the  statement  of  Mr.  Edwin 
Chadwick,  who,  hi  1844,  propounded  his 
views  with  the  authority  of  the  Board  of 
Health,  that  liquid  manure  was  at  all 
times  preferable  to  solid  manure,  and 
suitable  for  all  crops  and  all  soils,  we 
have  to  record  one  long  series  of  miser- 
able failures  in  the  attempt  to  find  ex- 
perimental proof  of  theoretical  estimates. 
The  failure  of  Mr.  Smith's  farm  (Dean- 
stone),  of  Mr.  Neilson's  farm,  of  Mr. 
Telfer's  farm,  of  Mr.  Kennedy's  farm, 
(Myremill),  of  Mr.  Huxtable's  farm,  of 
Mr.  Chamberlain's  farm,  of  Mr.  Little- 
dale's  farm,  and  of  Mr.  Mechi's  farm  (all 
of  which  cases  have  at  various  times 
been  held  up  as  wonderful  illustrations 
of  the  money  success  of  irrigation)  sup- 
ply the  unanswerable  answer  to  Mr. 
Edwin  Chadwick  and  his  school. 

The  Rugby  farm  was  pronounced  "un- 
remunerative "  by  its  first  manager, 


54 

whilst  it  was  abandoned  by  Mr.  Con- 
greve,  and  by  Mr.  Walker,  who  succeeded 
Mr.  Campbell.  The  story  of  one  and  all 
sewage  farms  is  a  history  of  commercial 
failure. 

The  irrigationists,  however,  still  point- 
ed those  who  doubted  the  commercial 
success  of  sewage  farming  to  the  Craig- 
en  tinny  meadows  in  Edinburgh.  We 
were  told  (correctly  no  doubt)  that  in 
good  seasons  £20  to  £30  worth  of  green 
produce  had  been  realized  per  acre  (say 
,£25  average).  But  it  is  no  secret: 

(1.)  That  in  these  meadows  the  quan- 
tity of  sewage  used  has  been  from 
10,000  to  13,000  tons  per  acre;  in  other 
words,  taking  the  produce  as  worth  £25, 
the  sewage  employed  had  a  value,  irre- 
spective of  rent  and  farming  expenses,  of 
less  than  ^d.  a  ton. 

(2.)  That  the  sewage  was  not  used 
continuously,  and  when  not  wanted  on 
the  land,  was  diverted  into  the  sea. 

Nothing  is  more  certain  than  that  the 
theoretical  value  calculation  of  sewage, 
based  on  the  supposition  that  the  ma- 


55 

nurial  elements  of  a  sewage,  extracted 
and  dried,  are  their  value  in  solution, 
must  be  regarded  as  an  extravagant 
dream  of  enthusiasm.  Such  calculations 
have  entirely  overlooked  the  effects  of 
dilution,  and  the  presence  of  a  mass 
of  worthless  material.  Nay,  more,  the 
"profligate  associates,"  as  they  have 
been  called  in  sewage,  are  not  merely 
worthless,  but  worse  than  worthless. 
Sewage  in  this  respect  is  not  singular. 
Thus,  whilst  rotten  farmyard  manure  may 
have  an  estimated  value  of  15s.,  its  prac- 
tical value  rarely  exceeds  one-half  its 
theoretical.  No  doubt  the  enthusiasts 
of  a  few  years  ago  have  learnt  a  lesson  at 
some  cost.  Mr.  Bailey  Denton,  admitting 
the  fallacy  of  old  calculations,  still  clings 
with  praiseworthy  consistency  to  some 
of  his  old  ideas  of  value.  "  Even,"  says 
he,  "  with  such  a  greatly  diminished 
value  (i.  e.,  If  d.  to  ^d.  a  ton),  the  country 
has  a  valuable  property  which  it  is  our 
duty  to  preserve." 

We  are  constantly  reminded,  moreover, 
of   the   success   of   irrigation   in   India, 


56 


Egypt,  Persia,  etc.  The  simple  applica- 
tion of  water  to  the  soil  in  dry  and  warm 
climates  increases  fertility.  Moreover, 
we  must  admit  that  sewage  has  a  higher 
manurial  value  than  mere  water.  But 
the  cases  are  not  comparable ;  a  climate 
having  the  temperature  of  our  own  with 
frequent  rain  (rain  falling  150  days,  on 
an  average,  out  of  365),  is  not  to  be  com- 
pared with  one  of  tropical  heat  and  of 
long  continued  drought.  The  sandy 
soil  of  Gennevilliers  or  of  the  Dantzic 
farm  are  no  cases  in  point.  Admitting 
as  a  fact  a  certain  manurial  value  in  sew- 
age, the  English  farmer,  it  is  certain,  would 
sooner  sacrifice  the  manurial  value  than 
be  compelled  always  to  have  the  water. 
For  two  difficulties  stare  him  in  the  face 
(and  a  sanitary  authority  demands  these 
conditions),  first,  to  be  compelled  to  take 
the  sewage  at  all  times  (day  and  night, 
Sundays  and  week  days)  all  the  year 
round  (summer  and  winter)  whether  his 
soil  wants  it  or  not,  or  whether  he  has 
any  crops  or  not  that  can  profitably  use 
it,  at  all  stages  of  their  growth,  seed  time 


57 


and  harvest,  and,  secondly,  so  to  utilize 
it  as  to  produce  an  effluent  which  at  all 
times,  all  the  year  round,  shall  neither 
produce  a  nuisance  nor  pollute  a  public 
watercourse.  In  times  of  frost — during 
the  heavy  rains  of  spring  and  autumn — 
the  farmer  finds  he  has  no  alternative  (his 
land  being  practically  impenetrable)  but 
to  let  the  sewage  pass  away  unpurified 
into  the  nearest  stream.  He  finds,  too, 
that  the  use  of  sewage  again  is  prejudi- 
cial during  the  maturity  and  ripening 
of  the  crops.  These  difficulties  were 
grasped  by  the  Parliamentary  Committee 
of  1862,  who  reported  that  "  it  was  de- 
sirable that  those  using  sewage  should 
have  a  full  control  over  it,  so  that  they 
might  apply  it  when  and  in  what  quanti- 
ties they  may  require." 

Local  authorities  have,  indeed,  learnt 
the  truth  of  these  statements,  since,  when 
they  adopt  an  irrigation  scheme,  they 
know  that  it  is  necessary  for  them  to  ac- 
quire land,  and  not  trust  to  the  farmers 
in  the  neighborhood. 

I  am  aware  that  the  difficulty  of  frost 


58 

is  supposed  to  be  met  by  the  increased 
temperature  of  the  sewage.  If  time, 
however,  be  allowed  for  the  ground  to 
be  aerated,  and  the  weather  be  so  cold  as 
to  freeze  it,  some  of  the  sewage  at  least 
must  flow  over  frozen  ground.  This  is 
the  dilemma.  Adopt  means  to  aerate 
your  ground,  and  it  will  become  frozen. 
Neglect  to  aerate  your  ground,  and  it  is 
useless,  or  practically  so.  The  difficulty 
of  storm  water  is  said  to  be  met  by  a 
certain  portion  of  land  being  kept  for 
storm  sewage,  and  possibly  planted  with 
osiers.  But  this  does  not  meet  the  case. 
Your  osier  beds  can  become  water-logged 
as  well  as  your  farm.  It  is  no  doubt  an 
advantage  to  have  a  reserve,  but  it  only 
meets  a  part,  and  a  very  small  part,  of 
the  real  difficulty. 

In  considering  the  question  of  work- 
ing cost,  quite  apart  from  the  expense 
of  preparing  the  land,  it  is  stated 
on  good  authority  (Local  Government 
Board  Report,  p.  33),  that  sewaged  land 
requires  more  horses  and  double  the 
amount  of  manual  labor  than  ordinary 


59 


arable  land.  This  means  greater  capital. 
"  To  properly  stock  (I  am  quoting  from 
the  report)  and  work  a  sewage  farm  upon 
which  the  main  produce  is  consumed, 
quite  five  times  the,  usual  amount  of 
money  will  be  needed.'' 

There  is  another  point  to  be  recorded, 
the  enormous  care  needed  in  the  manage- 
ment of  a  sewage  farm.  Dr.  Carpenter 
understands  this  when  he  laments  "  how 
mischievous  people  often  break  down  the 
carriers  and  other  works,  and  let  the 
sewage  run  where  it  ought  not  to  go — 
in  that  way,  getting  into  the  effluent 
water." 


We  have  admitted  a  certain  manurial 
value  in  sewage.  Before  we  proceed  to 
consider  the  question  of  producing  a 
good  effluent,  some  other  points  bearing 
on  its  fertilizing  powers  come  before 
us,  viz. : 

(1.)  The  methods  of  applying  sewage 
to  land. 

(2.)  The  soil  best  suited  for  irrigation. 


60 


(3.)  The  crops  most  suitable  for  a 
sewage  farm. 

(4.)  The  value  of  the  crops  so  grown. 

I. — THE  METHODS  OF  APPLYING  THE  SEW- 
AGE TO  LAND. 

Various  methods  have  been  suggested, 
such  as  simple  broad  irrigation,  as  prac- 
ticed at  Milan,  converting  the  field  into 
a  water  meadow  ;  and  subterranean  irri- 
gation, pipes  being  laid  sufficiently  deep 
to  be  beyond  reach  of  the  plow.  This 
may  be  called  upward  irrigation.  Both 
of  these  plans  have  been  tried  and 
abandoned.  Irrigation  by  hose  and  jet 
is  no  doubt  that  method  of  applying 
sewage  which  yields  the  best  results. 
(Smith  of  Deanstone,  Chad  wick,  Mechi, 
Telfer,  Kennedy.)  Professor  Way  says : 
"  If  you  ask  me  how  to  make,  regardless 
of  cost,  the  manurial  ingredients  of  the 
sewage  into  the  greatest  amount  of  pro- 
duce of  any  kind,  I  would  put  it  on  with 
pipes  and  hose  in  small  quantities  almost 
as  I  would  in  garden  cultivation,  as  if  I 
were  watering  it  with  watering  pots,  but 


61 


it  would  never  pay  you  to  do  it."  And, 
apart  from  this,  you  would  never  be  able 
to  get  on  the  land  the  quantity  that 
would  meet  the  sanitary  difficulty.  This 
failing,  sewage  has  to  be  brought  to  the 
highest  points  of  the  land  to  be  irrigated, 
conveyed  by  carriers  of  a  more  or  less 
permanent  character  into  some  form  of 
sewer  channels.  The  open  carriers,  or 
surface  channels,  may  be  mere  trenches, 
or,  if  it  be  desirable  that  they  should  be 
placed  above  the  ground,  constructed  of 
concrete  or  of  sheet  iron,  the  sewage  flow- 
ing in  large  or  small  volume,  as  required, 
upon  the  surface  of  theground.  Sometimes 
movable  troughs  are  used  (Carlisle),  but 
usually  the  sewage  is  run  through  open 
carriers,  and  merely  the  land  more  or 
less  flooded  by  the  carriers  being  dammed 
up  at  certain  parts.  Simple  contrivances 
only  are  required  to  turn  on  or  turn  off 
the  sewage  as  needed.  The  land  must 
of  course  be  so  leveled  and  drained  that 
the  sewage  may  flow  over  different  por- 
tions of  ground,  and  not  into  hollows, 
where  it  would  become  stagnant,  or  pass 


62 


away   without   undergoing   the    needful 
purification. 

II. — THE  SOIL  BEST   SUITED  FOB  IRRIGA- 
TION AND  FILTRATION. 

We  may  distinguish  three  cases : — 

1.  Very  porous  soils.     A  pure  sandy 
soil  has  had  its  advocates,  on  the  ground 
that  it   becomes   richer  every  year  that 
sewage  is  applied  to  it,  irrigation   thus 
serving  to  convert  poor  into  productive 
land   (Way).     Bagshot-heath    has  found 
favor  as  sewage  land  with  some,  on  the 
ground  of  its  porous,  sandy,  and  sterile 
character    (Lawes;    Paxton).     In    such 
soils,  however,  the  effluent  is  generally 
very  impure.     A  coarse,  gravelly  soil  may 
be  "  free,"  but  it  most  certainly,  as  a  rule, 
discharges  the  sewage  imperfectly  puri- 
fied,   on   account    of    its    non -retentive 
nature. 

2.  Heavy  clay  soils,  or  rather  soils  con- 
taining a  notable  proportion  of  clay,  were 
approved  by  Liebig,  on  the  ground  that 
clay  was  the  most  effective  soil  for  ab- 
sorbing   the    valuable     constituents    of 


63 


sewage,  viz. :  the  ammonia,  phosphoric 
acid  and  potash.  Liebig  considered  the 
success  of  the  Craigen tinny  meadows  to 
be  dependent  on  the  clay  in  the  soil- 
It  was  his  opinion  that  if  the  Maplin 
sands  were  to  be  used  as  irrigation  land, 
2,000,000  tons  of  clay  would  be  needed 
to  give  them  fertility  to  the  depth  of 
one  inch. 

A  soil  containing  such  a  proportion  of 
clay  as  to  retard  over-much  the  passage 
of  the  sewage  through  it,  acts  injuriously; 
in  other  words,  it  is  over-retentive — the 
fact  being  that,  to  get  the  best  effect  of 
nitration,  the  nitration  must  not  be  too 
slow.  The  effluent  is  in  such  cases 
usually  turbid  and  discolored. 

A  clay  soil  (e.  #.,  London  clay,  the  stiff 
clay  beds  of  the  new  red  sandstone,  and 
the  boulder  clay  overlying  the  Oxford 
clay)  are  impervious  to  water.  Such 
ground  may  be  utilized  by  burning  and 
mixing,  although  the  cost  of  such  treat- 
ment is  considerable. 

With  clay,  therefore,  we  may  have 
either  very  slow  nitration,  the  effluent 


64 


being  colored  and  turbid,  or  practically 
no  filtration  at  all.  Further,  such  soils 
are  specially  liable  to  crack  and  fissure, 
both  by  frost  and  extreme  heat ;  in  either 
case  the  sewage  would  run  through  the 
soil  in  an  absolutely  un  purified  condi- 
tion. 

3.  Soils  intermediate  between  sand 
and  clay.  Perhaps  a  sandy  loam,  or 
a  loam  with  a  small  portion  of  clay, 
is  that  soil  best  fitted  to  yield  a 
good  effluent  where  irrigation  or  filtra- 
tion through  land  is  practiced.  Bailey 
Denton  points  out  that  the  capacity  of 
soils  to  absorb  water  (e.  g.,  a  coarse, 
gravelly  soil)  is  no  criterion  of  its  cleans- 
ing capability.  On  the  contrary,  he  says, 
a  loamy  soil  having  sufficient  sand  to 
render  it  free  and  "  to  fill  it  with  close 
interstitial  spaces  for  aeration,  will  dis- 
charge a  superior  quality  of  purified 
water  by  the  under  drains."  The  best 
results  I  have  myself  seen  are  in  the  case 
of  soils  containing  about  86  to  90  per 
cent,  of  sand  with  a  little  clay. 

The  value  of  a  plant-bearing  soil  as  an 


65 

absorbent,  and  possibly  as  an  elaborator 
of  plant  food,  is  worth  considering.  Way 
supposed  the  absorbent  action  of  a  soil 
to  be  dependent  on  the  chemical  action 
of  certain  silicates  of  lime  and  alumina, 
which  fixed  the  alkaline  bases  and  allowed 
the  acid  constituents  (phosphoric  acid 
excepted)  to  pass  in  combination  with 
lime.  Liebig  states  that  an  acre -of  com- 
mon clay  soil,  4  inches  deep,  in  the 
neighborhood  of  Munich,  would  absorb 
2,076  Ibs.  of  ammonia,  1,910  Ibs.  of  pot- 
ash, 888  Ibs.  of  phosphoric  acid,  and  that, 
like  the  stomach,  which  fitted  food  for 
the  wants  of  the  ani  nal,  such  a  soil  fitted 
sewage  for  the  wants  of  the  plant.  Clay, 
in  his  experiments,  was  the  best  soil  for 
irrigation,  sand  the  worst,  turf  and  peat 
being  intermediate.  Voelcker  found  that 
clay  absorbed  potash  salts  and  ammo- 
nia freely  from  its  solution,  but  never 
completely,  the  ammonia  absorbed  being 
in  great  part  but  not  entirely,  capable  of 
removal  by  washing.  Sand  absorbed 
ammonia  and  potash  salts  imperfectly. 
Chalky  and  marly  soils  absorbed  and 


66 


rendered  insoluble  the  soluble  phos- 
phoric acid  more  powerfully  than  either 
clay  or  sand. 

Voelcker's  experiments  on  the  action 
of  various  soils  on  ammonia  show — 

A. — As  regards  free  ammonia  : — 

1.  That  all  soils  absorb  ammonia  from 
their  solution,  but  that  no  soil  absorbs  it 
completely 

2.  That  the  stronger  the  ammonia  so- 
lution, the  larger  the  absolute  quantity 
of  ammonia  absorbed,  whilst  the  weaker 
the  ammonia  solution,  the  larger  the  rela- 
tive quantity  of  ammonia  absorbed. 

3.  That  if  after  the  saturation  of  a  soil 
with   a   weak    solution    of    ammonia,    a 
strong  solution  be  applied,  the  soil  will 
absorb  more  ammonia  from   the  strong 
solution. 

B. — As  regards  salts  of  ammonia : — 

1.  That  the  soil  absorbs  the  ammonia, 
the  acid  of  the  salt  combining  with  the 
bases)  lime,  magnesia,  etc.)  present  in  the 
soil. 

2.  That   absorption    is   greater  with 


67 


strong  solutions  of  ammonia  salts  than 
with  weak  solutions. 

The  ammonia  absorbed  by  the  soil 
may  be  partly  removed  by  washing  with 
water,  but  the  quantity  capable  of  being 
thus  removed  is  always  relatively  less 
than  that  retained  by  the  soil — in  other 
words  the  absorptive  power  of  the  soil  to 
absorb  ammonia  is  relatively  less  than 
the  solvent  power  of  water  to  redis- 
solve  it. 

These  remarkable  results  are  chiefly 
dependent  on  the  alumina  and  hy- 
drated  oxide  of  iron  in  the  soil,  and  in 
lesser  degree  on  the  presence  of  lime  and 
other  bases. 

I  wish  to  remark  on  the  immense  ad- 
vantage in  an  irrigation  farm  of  ferrugi- 
nous earth.  I  have  seen  a  case  where  a 
very  good  effluent  was  obtained  by  the 
accidental  circumstances  of  a  small  area 
(small,  that  is,  in  comparison  to  the  en- 
tire farm)  containing  a  large  quantity  of 
an  iron  deposit. 

The  composition  of  irrigated  as  com- 
pared with  non-irrigated  soils  has  been 


68 


on  many  occasions  contentious  matter  in 
our  courts,  and  the  subject  of  numerous 
investigations.  The  top  few  inches  of 
an  irrigated  farm  presents  no  doubt  a 
very  marked  difference  from  the  underly- 
ing soil,  such  difference  being  dependent 
partly  on  the  nature  of  the  soil,  partly  on 
the  method  of  irrigation,  but  more  par- 
ticularly upon  how  far  the  suspended 
matters  have  been  removed  before  the 
application  of  the  sewage  to  land,  and  the 
extent  to  which  intermittency  of  action 
has  been  practiced.  If,  however,  the  top 
inch  of  the  land  be  carefully  scraped  off, 
the  difference  of  the  composition  of  sew- 
aged  and  non-se  waged  ground  will 
probably  be  found  to  be  small.  As  re- 
gards nitrates,  phosphates  and  chlorides, 
the  difference  is,  as  a  rule,  absolutely  nil. 
Perhaps  there  may  be  a  slightly  increased 
amount  of  oxidizable  organic  matter,  but 
even  this  is  by  no  means  invariable, 
whilst  at  a  depth  of  eighteen  inches,  it  is 
a  very  rare  thing  to  find  any  marked 
alteration  of  composition.  It  is  certain, 
therefore,  that  given  land  of  ever  so 


69 


suitable  a  character  as  u  sewage  purifier, 
its  powers  are  not  those,  agriculturally, 
of  a  storage  battery. 

Any  excess  of  sewage  over  that  which 
the  plant  can  utilize  at  the  time  is,  so  far 
as  commercial  profit  is  concerned,  wasted, 
passing  off  inlo  the  subsoil  drainage 
partially  or  wholly  purified.  As  a  fact, 
the  land  does  not  store  in  any  quantity 
the  manurial  elements  for  the  use  of 
future  crops.  The  fertility  of  a  given 
area  is  not  10  times  greater  by  the  appli- 
cation of  the  sewage  of  1,000  persons, 
than  it  would  be  by  the  application  of 
the  sewage  of  100.  In  fact,  it  is  no 
better  and  no  worse.  The  difference  is 
to  be  sought  in  the  effluent,  not  in  the 
land.  The  Craigentinny  meadows  are 
still  sandy  and  poor,  despite  of  all  the 
sewage  put  upon  them.  The  land,  not- 
withstanding all  that  has  been  done  for 
it,  still  contains  less  than  fifteen  parts  of 
organic  matter  in  a  thousand. 

But  how  far  is  absorption  dependent 
on  the  strength  of  the  manurial  fluid  ap- 
plied ?  Voelcker's  investigations  on  this. 


70 

point  have  been a  referred  to  in  detail. 
His  experiments  show  that  when  manor- 
ial elements  in  a  weak  solution  like  sew- 
age is  applied  to  the  soil,  it  merely 
oxidizes  the  nitrogen  and  strains  the 
fluid,  the  resulting  nitrates  flowing  away, 
unless  vegetation  is  growing  at  the  time, 
when  the  elements  of  the  sewage  may  be 
appropriated.  But  more  than  this,  his 
experiments  show  that  a  weak  sewage 
may  actually  remove  from  a  soil  upon 
which  there  is  no  vegetation,  the  rna- 
nurial  ingredients  already  present  in  it. 

That  the  total  soluble  nitrogen  of  sew- 
age may  be  found  in  the  effluent  as 
nitrates  when  the  sewage  is  applied  to 
land  where  there  is  no  vegetation  or 
where  vegetation  is  inactive,  I  have  many 
times  verified  by  analysis. 

III.— CROPS    MOST    SUITABLE    ?OR    IRRI- 
GATION. 

Nearly  all  agree  that  the  most  profit- 
able application  of  sewage  is  to  pasture 
land,  osiers,  and  Italian  rye  grass.  Way 


71 

says  that  its  application  to  grass  land  is 
the  only  profitable  way  of  dealing  with 
it — in  other  words,  by  feeding  it  into 
milk  or  flesh,  and  so  getting  a  manage- 
able manure. 

Bailey  Denton  holds  a  different  view, 
considering  that  a  the  less  the  sewage 
farmer  has  to  do  with  stock  the  better." 
He  is  of  opinion  that  the  cultivation 
of  grass  is  unprofitable. 

And  here  I  may  refer  to  the  greediness 
with  which  cattle  feed  on  sewage-irrigated 
pasture.  Mechi  states  that  cattle  will 
follow  the  hose  and  feed  on  the  grass  wet 
with  sewage.  Many  who  gave  evidence 
before  the  Parliamentary  Committee  on 
the  sewage  of  towns  testified  to  the  same 
effect,  the  committee  reporting  that "  the 
evidence  proves  that  cattle  of  all  sorts 
appear  to  prefer  sewaged  grass  to  all 
others,  and  will  eat  it  within  a  few  hours 
of  its  being  dressed  with  sewage."  And 
I  beg  your  attention  to  this  fact  in  pass- 
ing, for  I  shall  refer  to  it  again  when  I 
speak  of  the  dangers  incident  to  eating 
the  meafc  of  animals  fed  on  sewage  pro- 
duce. 


I  would  note,  too,  thafc  there  is  evi- 
dence to  show  that  a  damp  and  sodden 
condition  of  ground,  such  as  is  common 
in  a  sewage  farm,  is  peculiarly  favorable 
for  the  production  of  the  "  liver  fluke  "  of 
sheep  (Diatoma  hepaticum),  a  disease 
occasioning  great  fatality.  This  danger 
of  irrigation  is  not  undeserving  of  atten- 
tion. 

Roots. — Some  have  advocated  irriga- 
tion for  root  crops  in  dry  weather  (Camp- 
bell, of  Kugby).  The  mangold-wurtzel 
does  well  in  a  sewage  farm. 

Miller,  of  Edinburgh,  is  against  the 
use  of  sewage  for  roots,  since  he  found 
it  made  furrows  and  channels  in  arable 
land,  and  washed  the  roots  of  plants 
bare. 

Bailey  Denton  advocates  the  growing 
of  roots  (mangolds,  beets,  turnips,  car 
rots,  parsnips,  potatoes  and  onions)  as 
better  crops  for  sewage  land  than  the 
cultivation  of  grass. 

Cereals.—  Some  consider  sewage  suit, 
able  for  wheat.  Mechi  advocated  its  use, 
although  not  directly  to  the  land  so  used 


73 

(otherwise  the  wheat  grows  too  luxuri- 
antly and  fills  too  easily)  but  to  a  preced- 
ing grass,  root,  or  clover  crop. 

The  majority  of  authorities  disapprove 
of  its  application  to  arable  land,  or  of  its 
use  for  cereals,  roots,  etc.  Voelcker  says, 
"It  is  quite  unfit  for  cereals  after  the 
grassy  state,  because  of  its  forming  straw 
instead  of  grain,  and  checking  the  ripen- 
ing process."  Lawes,  Way,  Congreve  (of 
Rugby),  have  expressed  themselves  to 
much  the  same  effect. 

Its  application  to  corn  crops  was  tried 
at  Watford,  Rugby  and  Alnwick,  but 
abandoned. 

Bailey  Den  ton  advocates  the  production 
of  straw  upon  a  sewage  farm  as  advanta- 
geous for  feeding  stock,  although  the 
quantity  of  grain  is  small. 

Voelcker  condemns  its  use  for  market 
produce,  "as  it  clogs  the  soil  and  kills 
the  plant." 

Bailey  Denton  specially  advocates  the 
cultivation  of  cabbages  on  sewage  farms. 
I  remember  being  told  that  they  had 
tried  growing  rhubarb  at  Alder  shot,  but 


74 


that  they  abandoned  it  because  nobody 
would  eat  it  a  second  time,  owing  to  its 
rank  sewage  flavor. 

At  the  Brussels  International  Con- 
gress (1876)  a  collection  of  vegetables 
were  shown,  said  to  have  been  grown  in 
fields  irrigated  by  the  sewage  of  Paris. 
There  was  a  curious  silence  as  to  the  cost 
of  production. 

Liebig,  arguing  on  the  quantities  of 
ammonia  and  phosphoric  acid  in  sewage, 
in  comparison  to  the  quantity  of  potash, 
considers  sewage  less  adapted  for  grass 
crops  than  for  pasture  land.  Say  4  tons 
of  good  hay  (=  12  tons  of  grass)  is 
grown  on  an  acre  of  land  per  annum. 
This  4  tons  abstracts  from  the  land : — 

Nitrogen 141.61bs.  (=ammonial721bs.) 

Phosphoric  acid    72      " 
Potash  124      " 

To  get  124  Ibs.  of  potash  you  must  have 
2,400  tons  of  sewage.  This  contains : — 

Nitrogen 451.07  Ibs.  (= ammonia 

Phosphoric  acid  109.6     "  547.73  Ibs.) 

Potash..  .  124 


75 


Now  in  accordance  with  the  law  that 
"the  effect  of  all  the  constituents  of  a 
manure  is  but  the  effect  of  that  one  of 
them  which,  in  comparison  with  the  wants 
of  the  plant,  is  present  in  the  smallest 
quantity,"  it  follows  that  375.73  Ibs  of 
ammonia,  and  37.6  Ibs.  of  phosphoric 
acid,  are  not  merely  wasted,  but  act  in- 
juriously by  clogging  the  soil  and  killing 
the  plants.  On  this  ground  he  advocates 
adding  to  the  sewage  potash  and  phos- 
phoric acid  in  proportion  to  the  require- 
ments of  the  crop,  thus  lessening  the 
sewage  required,  and  increasing  general 
fertility.  Thus  Liebig  argues  that  sew- 
age should  always  be  used  in  conjunc- 
tion with  richer  manures,  guano  bein£ 
rich  in  phosphates  and  ammonia,  but 
poor  in  potash ;  farmyard  manure  being 
rich  in  potash  but  poor  in  phosphates 
and  ammonia  ;  sewage  occupying  an  in- 
termediate position.  The  following  table 
will  serve  to  illustrate  his  views : — 


76 


Phosphoric     Am- 
Potash    acid       monia 
Ibs.       Ibs.          Ibs. 

193  tons  of  sewage  yield 10.      8.8.    44.1 

2,0231bs.offarmyardmanure.lO  .       9.0  .     14.9 
1,672  Ibs.  of  Peruvian  guano  10  .  200.5  .  142.3 

Voelcker  scarcely  endorses  these  views, 
for  he  says  if  the  soil  itself  contains  the 
elements  of  fertility,  sewage  has  no 
more  value  than  so  much  water ;  but  if  it 
be  poor  and  barren  then  the  application 
of  sewage  will  produce  crops  of  grass 
when  nothing  else  of  any  agricultural 
value  will  grow  upon  it. 

IV. — VALUE  OF  CROPS  GROWN  ON  SEWAGE- 
IRRIGATED  FARMS. 

It  must  be  admitted  that  the  size  and 
weight  of  roots  and  succulent  vegetables 
grown  on  a  sewage  farm  are  often  con- 
siderable. Thus  enormous  cabbages, 
turnips,  celery,  etc.,  are  often  shown  as 
sewage-grown.  But  sewage  produce  is 
best  described  as  dropsical,  i.  e.,  the  per- 
centage of  moisture  in  sewage-grown 
produce  is  far  higher  than  in  the  case  of 


77 


ordinary  market  produce.  (This  fact 
was  proved  by  Lawes  in  his  experiments 
at  "Rugby  Farm.)  This  being  the  case, 
sewage  produce  is  difficult  to  dry,  and 
prone  to  decompose.  It  must  be  con- 
sumed fresh,  and  on  the  spot,  for  it  will  not 
stand  being  carried  any  distance  to  mar- 
ket. Dr.  Voelcker  is  definite  on  this 
point.  Irrigated  land,  it  is  certain,  does 
not  yield  so  nutritious  a  product  as 
natural  pastures.  If  you  want  good 
produce,  you  must  be  content  with  small 
quantity. 

PERCENTAGE  COMPOSITION  OF  DRY  SUBSTANCES. 


H.'O. 

1 

1 
afcS 

J. 

**  Sc 

"'  a  *  "  § 

M   CO  0 

sg 

2|||2j| 

III 

0 

0 

§  . 

8 

g 

* 

CO 

d 

05 

Nitrogenous  substances.  . 

11.16 

17.58 

18.  b7 

19.66 

Fatty  matter  (ether  ex- 

tracts)     

3.41 

4.13 

3.95 

404 

Woody  fiber             .       .  i  29.  08  28  21 

28.32 

28.13 

Other  non-nitrogenous 
matters  46.73  39.09 

38,08 

3691 

Mineral  matter  (ash)  

9.62 

10.99 

11.28 

11.26 

78 


Passing  to  the  solid  matter  itself,  a 
larger  proportion  of  nitrogen  was  found 
in  the  sewaged  than  in  the  unsewaged 
produce,  and  the  larger  the  quantity  of 
sewage  applied,  the  larger  became  the 
nitrogenous  constituents  of  the  vegeta- 
tion. 

But  here  arises  the  important  ques- 
tion, "Are  nitrogenous  constituents  the 
true  measure  of  the  nutritive  quality  of  a 
produced"  To  this  Voelcker  replies, 
"No.''  On  the  contrary,  nutritive  prop- 
erties depend  on  proper  maturation, 
whilst  an  excessive  quantity  of  nitroge- 
nous produce  indicates  unripeness,  i.  6.,  a 
deficiency  of  sugar. 

I  have  thus  far  limited  myself  almost 
entirely  to  a  consideration  of  the  manur- 
ial  value  of  sewage.  We  must  now  con- 
sider, in  connection  with  manurial  value, 
the  second  condition  of  effective  sewage 
treatment,  viz.  :  the  production  of  a  good 
effluent. 

There  now  arises  the  important  ques- 
tion, how  much  sewage  can  properly 
(qua  agricultural  success)  and  safely  (qua 


79 


sanitary  success)  be  applied  to  a  given 
area  of  land. 

There  are  two  ways  of  applying  sew- 
age to  land — 

1.  Surface  irrigation,  or  the  distribu- 
tion of  sewage  over  as  many  acres  as  it 
will  wet,  having  in  view  a  maximum  plant 
growth. 

2.  Intermittent  down  ward  nitration. 

I. — SURFACE  IRRIGATION. 

And  here  one  fact  is  certain,  the  agri- 
cultural and  the  sanitary  aspects  of  the 
question  are  not  in  accord.  To  realize 
an  agricultural  success,  the  farmer  says, 
apply  at  proper  times  and  seasons  a  large 
quantity  of  sewage  (and  within  reason 
the  larger  the  better)  to  your  land.  To 
realize  a  sanitary  success,  the  sanitarian 
says,  apply  continuously  as  small  a  quan- 
tity as  possible.  If  sewage  be  put  upon 
a  soil  in  larger  volume  than  1,500  tons 
per  acre  per  annum,  even  when  there  is 
actively  growing  rye  grass  upon  it,  the 
subsoil  water  is  certain  to  pass  away  foul 


80 

(Way).  It  was  found  at  the  Anerley 
School  farm  that  the  same  crop  of  grass 
was  obtained  when  1,500  tons  of  sewage 
per  acre  was  applied  by  hose  and  jet,  as 
when  8,000  to  9,000  tons  were  supplied 
by  open  carriers ;  but  that  in  the  latter 
case  the  effluent  water  was  almost  as  foul 
as  the  sewage  (Westwood).  At  Rugby, 
it  was  recorded  that  with  3,000  tons  of 
sewage  per  acre,  a  yield  of  22  tons  of 
grass  was  obtained,  whilst  with  6,000 
tons  of  sewage  a  yield  of  28  tons  of 
grass,  and  with  9,000  tons  of  sewage  a 
yield  of  32  tons  of  grass  only  was  ob- 
tained (Lawes).  The  conclusion  is  irre- 
sistible. There  is  a  limit  to  the  quantity 
of  manurial  elements  that  the  soil  and 
plants  are  capable  of  appropriating.  Ex- 
ceed this  limit,  and  any  quantity  in  ex- 
cess must  pass  away  in  a  more  or  less 
unoxidized  form. 

As  regards  the  quantity  of  sewage  that 
is  safe  and  proper  to  apply  to  land,  I 
find  authorities  differ  between  100  tons  and 
40,000  tons  per  acre  per  annum  ;  a  differ- 
ence, in  other  words,  between  2  and  800 


81 


persons  per  acre.  Thus  an  authority 
"  of  great  weight "  expresses  an  opinion 
that  300  tons  of  sewage  per  acre  per  an- 
num would  accomplish  as  much  as  the 
10,000  tons  he  had  applied.  Another 
authority  considered  the  Kugby  farm  in- 
ferior to  the  Edinburgh  meadows,  be- 
cause in  the  former  from  3  to  9,000  tons 
of  sewage  per  acre  only  was  applied, 
whereas  in  the  latter  10  to  12,000,  and 
even  30  to  40,000  tons  have  been  used. 
Mr.  George  Shepperd  and  Mr.  Mechi 
considered  100  tons  of  sewage  per  acre 
per  annum  sufficient  (or  the  manure  of 
two  persons).  The  latter  lived  to  find 
his  estimate  erroneous,  increasing  his 
quantities  at  first  to  500,  and  finally  to 
^,000  tons  per  acre  for  green  crops. 
Miles,  of  Bristol,  reported  that  two  per- 
sons per  acre  gave  good  results,  whilst 
Mr.  Thomas  Ellis  considered  (and  in  this 
Mr.  Brady,  the  chairman  of  the  Select 
Committee  on  Sewage,  agreed)  600  tons 
of  sewage  (or  the  produce  of  a  dozen 
people)  advisable. 

Mr.  W.  Hope  and  Mr.    Westwood,  of 


82 


the  school  farm  at  Anerley,  considered  an 
acre  of  land  was  required  for  every 
twenty  or  thirty  people  (1,000  to  1,500 
tons  of  sewage  per  annum),  for,  said  Mr. 
Westwood,  "if  more  than  this  be  used, 
it  runs  away  into  the  drains  and  fouls  the 
stream."  This  he  found  to  be  the  case 
when  8,000  or  9,000  tons  per  acre  was 
applied  to  land  cultivated  with  rye  grass. 
Liebig  considered  2,430  tons  of  sewage 
sufficient  for  meadow  land  to  yield  12 
tons  of  grass  (4  tons  of  hay)  per  acre. 
He  adds,  a  soil  saturated  with  manure 
not  only  fails  to  increase  the  crop,  but, 
in  the  case  of  roots,  is  positively  hurtful. 
The  Earl  of  Essex  (Chairman  of  the 
Commission  to  inquire  into  the  best 
method  of  utilizing  sewage)  after  many 
trials  at  Watford,  decided  that  5,000  to 
6,000  tons  a  year  was  desirable  to  each 
acre  for  Italian  rye  grass,  but  that  600 
tons  to  each  acre  was  sufficient  in  the 
case  of  meadow  land.  Voelcker  fixes 
2,000  to  4,000  tons  per  acre  for  better 
kind  of  lands,  and  8,000  to  10,000  tons  for 
sandy  soils,  stating  "that  he  has  nowhere 


83 


seen  such  small  quantities  as  300  or  400 
tons  per  acre  produce  any  remunerative 
effect."  Way  likewise  fixes  100  persons 
to  the  acre,  provided  the  land  be  grass 
land,  estimating  that  30,000  acres  of  land 
would  be  required  if  the  sewage  of 
3,000,000  people  had  to  be  dealt  with. 

Sir  E.  Rawlinson  states  the  case 
thus : — 

"The  means  which  have  been  found 
in  practice  to  answer  are  as  under  stated, 
namely,  for  flood  irrigation  about  one 
statute  acre  to  100  of  population  of  a 
fully  water-closeted  town,  but  there  can- 
not be  any  hard  and  fast  rale." 

In  nineteen  irrigated  towns,  according 
to  Professor  Robinson,  there  is  an  aver- 
age of  137  persons  to  each  acre  (=  to 
5,128  gallons  per  acre  per  day,  or  38 
gallons  of  sewage  per  head  of  the  popu- 
lation per  day).  Mr.  McKie,  of  Carlisle, 
records  the  average  of  53  towns  as  98 
persons  to  each  acre  (—to  3,826  gallons 
of  sewage  per  acre  per  day). 

Lawes  and  Rawlinson  also  agree  that 
an  acre  of  land  is  required  for  every  100 


84 


people  (or  5,000  tons  of  sewage  per 
year),  a  view  agreed  to  in  the  main  by 
Bailey  Denton,  who  fixes  100  to  150 
people,  according  to  the  porosity  of  the 
soil,  lighter  soil  taking  the  sewage  more 
freely  than  heavy.  In  Bailey  Denton's 
opinion,  however,  extra  land  is  needed 
for  giving  rest,  and  for  permitting  alter- 
nate cropping. 

The  difficulties,  it  will  be  seen,  are 
tremendous.  For  commercial  profit  the 
sewage  must  not  be  less  than  5,000  tons 
per  acre — for  sanitary  efficiency  (i.  e.,  to 
prevent  nuisance),  the  quantity  must  not 
exceed  1,500 — i.  e.,  a  minimum  of  100  is 
necessary  to  pay — whilst  30  is  the  maxi- 
mum to  escape  prosecution. 

II. — INTERMITTENT  DOWNWARD  FILTRATION. 
The  difficulty  of  securing  efficient  land 
for  surface  or  broad  irrigation  pressed 
hard  on  the  irrigationists.  Dr.  Frank- 
land  and  others  saw  that  the  larger  the 
population  of  a  town,  not  only  the  less 
land  there  was  within  a  reasonable  dis- 
tance, but  the  more  costly  such  land  be- 


85 

came.  Irrigation  was  doomed  unless  the 
land  difficulty  could  be  overcome,  and 
some  method  adopted  whereby  a  large 
volume  of  sewage  could  be  concentrated 
on  a  small  area. 

Dr.  Frankland's  laboratory  experiments 
of  1870,  with  known  quantities  of  differ- 
ent soils,  gave  birth  to  the  process 
known  as  "Intermittent  Downward  Fil- 
tration." For  this  purpose  it  was  stated 
to  be  necessary — (1)  to  have  a  suitably 
constituted  soil  which  will  act  as  a  filter ; 
that  is,  a  soil  not  too  open,  so  that  any- 
thing may  pass  through,  but  not  too 
close,  so  that  nothing  may  pass  through. 
(2.)  To  have  the  land  deeply  drained, 
say  at  a  depth  of  6  feet,  so  as  to  allow  a 
considerable  distance  for  percolation. 
This  constituted  filtration  as  opposed  to 
irrigation.  The  land  becomes  an  oxi- 
dizing instrument,  to  burn  the  impurities, 
and  so  transform  them  into  harmless 
gases,  rather  than  a  mere  separating  ma- 
chine. To  obtain  the  best  effects  of 
oxidation,  and  to  keep  the  land  in  the 
most  effective  condition,  the  sewage  must 


86 

be  applied  intermittently,  i.  e.,  with  regu- 
lated intervals  of  rest,  to  give  time  for 
air  to  go  into  the  ground  as  the  water 
runs  out,  thus  fitting  it  for  a  fresh  dose 
of  sewage.  Intermittent  filtration,  Dr. 
Frankland  would  say,  is  a  copy  of  nature 
in  the  lung  action  of  respiration,  alter- 
nately receiving  and  expelling  air. 
This  intermittent  work  avoids,  he  would 
contend,  the  clogging  of  the  soil,  and 
secures  its  efficient  and  frequent  aeration. 
By  such  means  Dr.  Frankland  stated  that 
the  sewage  of  3,300  people  could  be 
treated  on  one  acre  of  land. 

Let  me  endeavor  to  give  an  illustration 
of  the  method  of  working  the  intermit- 
tent downward  filtration  system. 

Suppose  a  population  of  9,900,  with 
three  acres  of  suitable  land  suitably 
drained.  Each  acre,  for  purposes  of 
work,  is  subdivided  into  four  parts,  the 
sewage  of  3,300  being  placed  successively 
for  a  period  of  six  hours  on  each  quarter 
acre.  Thus  each  quarter  acre  receives 
the  sewage  of  3,300  people  for  six  hours, 
eighteen  hours  rest  being  allowed  before 


87 


it  receives  another  dose.  Some  have 
suggested,  in  further  development  of  the 
idea  of  intermittency,  that  one  of  the 
three  acres  might  be  used  per  year  for 
the  9,900,  so  that  each  acre  would  have 
two  years  during  which  it  might  the  more 
perfectly  recover  itself,  whilst  each  quar- 
ter acre  of  the  one  acre  in  use  for  the 
year  would  have  eighteen  hours  rest  out 
of  the  twenty-four.  It  is  no  misnomer 
to  call  this  "intensified  irrigation/' 

But  Dr.  Frankland's  arguments  were 
based  on  laboratory  experiments.  The 
varying  effects  of  the  varying  qualities  of 
sewage  on  the  one  hand,  and  the  enor- 
mous differences  in  land,  as  regards  its 
capability  of  absorption  and  filtration,  on 
the  other,  seem  to  have  been  very  im- 
perfectly considered.  Nor  were  the  diffi- 
culties arising  from  subsoil  water  taken 
into  calculation,  nor  the  density  of  the 
soil  in  the  laboratory  experiments,  as 
compared  with  its  density  in  the  natural 
state.  I  am  fully  aware  that  Dr.  Frank- 
land  would  say  that  the  estimate  of  3,300 
to  an  acre  supposes  proper  land — prop- 
erly drained — properly  leveled. 


88 


It  is  right,  too,  we  should  note  that 
Dr.  Frankland  has  from  the  first  insisted 
that  intermittent  downward  filtration  in- 
volved the  sacrifice  of  the  manurial  value 
of  the  sewage,  the  area  of  ground 
being  too  small,  and  the  quantity  of  sew- 
age too  large,  to  make  it  pay.  This  view, 
however,  Mr.  Bailey  Denton  in  no  way 
endorses;  on  the  contrary,  he  considers 
that  the  system  of  the  intermittent  appli- 
cation of  sewage  to  land  in  no  way  inter- 
feres with,  but  actually  assists,  farming 
operations. 

Both  Dr.  Frankland  and  Mr.  Bailey 
Denton  agree  in  considering  the  removal 
of  the  suspended  matter  in  the  sewage 
before  its  application  to  the  land  to  be 
unnecessary.  Mr.  Bailey  Denton,  how- 
ever, advocates  the  use  of  furrows 
(rather  than  flooding  the  land),  partly  as 
a  means  of  preventing  the  clinging  of 
solid  sewage  matter  to  the  stalks  and 
leaves  of  plants,  and  partly  with  the  ob- 
ject of  bringing  the  sewage  into  contact 
with  the  roots,  which  are  the  active  ab- 
stracting agents  of  manurial  worth.  In- 


89 


deed,  Bailey  Denton  goes  so  .  far  as  to 
say  that  the  presence  of  the  suspended 
sludge  in  the  sewage  is  an  advantage 
rather  than  a  bar  to  its  application  to 
land.  By  making  some  furrows  of  greater 
depth  than  others,  he  renders  these  the 
receptacles  of  the  solid  matters.  The 
sludge,  he  says,  "  consists  of  vegetable 
and  animal  substances  which  are  perish- 
able, mixed  with  earthy  and  mineral  sub- 
stances, which  are  not  perishable.''  It  is 
only  necessary  to  remember  this  uto 
realize  the  fact  that  they  cannot  possibly 
clog  the  land  when  dry.  The  most  mi- 
nute particles  consist  of  fine  road  sand 
which  floats  on  in  the  liquid  after  the 
heavier  detritus  has  deposited  itself. 
When  these  perishable  and  imperishable 
substances  find  their  way  into  the  soil, 
they  must  each,  from  their  nature,  ob- 
viously add  to  its  porosity,  inasmuch  as 
the  perishable  substances  leave  open 
spaces  as  they  decay,  whilst  the  imper- 
ishable substances  from  their  gritty  na- 
ture necessarily  help  to  increase  its  filter- 
ing capabilities.  So  long  as  the  sludge 


UNIVERSITY 


90 


is  wet  it  impedes  absorption  to  a  certain 
extent,  but  when  once  dried,  and  the 
land  broken  up  by  the  plow,  it  not  only 
ceases  to  uphold  the  liquid,  but  natural- 
ly and  permanently  helps  to  let  it  into 
and  through  the  soil."  In  other  words, 
by  digging  the  sludge  into  the  soil,  Mr. 
Denton  contends  that  the  soil  is  ren- 
dered more  percolative  than  before. 
There  may  be  something  in  this  view. 
But  how  often  have  we  seen,  in  practical 
working,  sewage  being  applied  to  land, 
clogged  by  large  masses  of  black  albu- 
menous  matters,  the  result  of  previous 
irrigations,  closely  adhering  to  the  soil, 
impeding  absorption,  and  lessening  the 
surface  through  which  the  water  can 
pass  into  the  ground.  Mr.  Denton  says, 
"  the  sludge  must  then  be  allowed  to  dry, 
and  when  in  a  fit  condition  dug  in.''  But 
in  the  act  of  drying  comes  the  nuisance. 
In  hot  weather  it  means  putrefaction 
(Mr.  Denton  calls  it  decomposition  of 
perishable  substances),  and  with  putre- 
faction comes  a  stink,  besides  which  it 
is  in  the  act  of  evaporation  that  dangers 


91 


occur  from  detrimental  matters  being 
carried  bodily  into  the  air.  In  filter 
beds,  we  know  full  well  that  the  surface 
of  the  filter  bed  is  that  part  most  affect- 
ed, and  further  that,  for  efficiency,  the 
surface  of  the  filter  bed  needs  frequent 
removal  and  cleansing,  whilst  irrigated 
land  shows  neither  to  the  eye  nor  to 
chemical  analysis  much  indication  of  any 
excess  of  organic  impurity  a  few  inches 
from  the  surface. 

I  admit  to  the  full  the  power  of  soil  to 
purify  sewage  by  oxidation.  I  admit, 
moreover,  the  advantage  of  intermit- 
tency  of  action,  i.  e.,  of  intervals  of  rest 
alternating  with  intervals  of  work.  The 
entire  success  of  the  process,  however, 
depends  on  perfect  aeration  during  rest, 
to  fit  the  soil  for  its  next  period  of  work. 
My  experiments  lead  me  to  doubt  the 
efficiency  of  a  rest  of  18  hours  only, 
even  when  the  sewage  has  had  the  solids 
in  suspension  removed.  But  of  this  I 
am  certain,  that  when  the  suspended 
solids  have  been  allowed  to  remain  in  the 
sewage,  the  glutinous  constituents  of  the 


92 


sewage,  together  with  the  papier  mache 
material  in  solution,  clogs  the  ground 
with  an  impervious  covering,  whereby 
the  entrance  of  air  is  very  much  retard- 
ed. Further,  the  sewage,  when  applied 
after  the  period  of  rest,  cannot  flow 
through  the  ground  on  the  surface  read- 
ily, on  account  of  the  glutinous  layer 
and  papier  mavhe  film.  Thus,  as  a  re- 
sult, the  period  of  rest  fails  to  become, 
qua  the  soil,  a  period  of  aeration.  This 
condition  will  be  aggravated  should  the 
effluent  water,  from  any  circumstance, 
not  flow  freely  away.  Thus  the  very 
condition  of  success  may  be,  and  as  I 
know  often  is,  thwarted  during  the 
period  of  rest,  as  the  result  of  the  pre- 
ceding period  of  work. 

Difficulties  of  a  practical  nature 
crowd  upon  us  in  considering  this  meth- 
od of  treatment.  Three,  at  any  rate, 
may  be  noted : 

1.  The  cost  of  preparing  the  land  for 
the  work. 

2.  The   difficulty   of    securing  proper 
land,  or  of  ensuring  its  effective  working 


93 


at  all  times,  in  all  weathers,  with  all 
kinds  of  sewage,  and  under  all  circum- 
stances. 

3.  The  fact  that  much  of  the  solid 
filth  of  the  sewage  will,  unless  previous- 
ly removed,  accumulate  on  the  surface, 
where  it  undergoes  decomposition  and 
becomes,  especially  in  hot  weather,  a 
formidable  nuisance. 

Intermittent  downward  filtration  had 
its  birthplace  in  the  laboratory.  Whether 
the  earth  used  were  cube  feet  or  yards, 
or  six  foot  tubes,  many  details  besides 
this  mere  statement  of  the  work  accom- 
plished are  necessary.  Was  the  earth 
used  surface  earth  ?  How  was  the  sew- 
age collected?  Was  the  earth  exposed 
to  the  modifying  influence  of  wind,  light 
and  rain  ?  How  long  was  the  earth 
used — a  week,  a  month,  a  year,  or 
longer?  It  is  to  be  feared  that  a  new 
birth  in  sewage  treatment  needs  a  less 
cramped  cradle  than  a  London  labor- 
atory. You  cannot  learn  how  to  direct 
an  army  in  the  field  by  practicing  with 
toy  soldiers.  No  laboratory  experiment 


94 


pure  and  simple  can  teach  sewage  treat- 
ment. 


We  now  turn  to  the  hygienic  aspect  of 
sewage  irrigation.  I  shall  speak  of  three 
classes  of  effects  rendering  sewage  irri- 
gation dangerous  to  the  public  health  : 

1.  Offensive  and  injurious  emanations. 

2.  Pollution  of  subsoil  water. 

3.  Distribution   of    un defecated    sew- 
age containing  the  ova  of  entozoa. 

I. — OFFENSIVE  AND  INJUKIOUS  EMANATIONS. 

Of  such  emanations,  the  evidence  is 
ample.  The  River  Pollution  Commis- 
sioners admit  that  odors  do  arise  with 
land  irrigated  with  sewage,  day  after 
day,  for  years.  The  Craigentinny  mea- 
dows, near  Edinburgh,  can  only  be  de- 
scribed as  filthy,  emitting  a  stink  hardly 
endurable.  The  surgeon  to  the  barrack 
adjoining  the  meadows,  described  the 
stench  (1868)  as  "sickening."  Of  the 
Croydon  Sewage  Farm,  at  Beddington, 
Dr.  Creasy,  Surgeon  to  the  Orphan  Asy- 
lum at  Beddington,  stated  that  "  typhoid 


95 


fever  had  been  in  every  cottage  on  the 
estate  " — every  disease,  in  fact,  assuming 
a  particular  type,  accompanied  by  what 
is  called  a  "sewage  tongue."  In  fact,  the 
stink  of  sewage-irrigated  ground,  and 
the  malarious  effects  of  the  sewer  gases 
evolved,  are  matters  of  frequent  com- 
plaint and  litigation.  Dr.  Clouston 
traced  an  outbreak  of  dysentery  in  the 
Cumberland  and  Westmoreland  Asylum 
to  the  effluvia  from  a  sewage  farm. 

There  is,  too,  a  remarkable  statement 
by  Copland,  that  the  effects  of  sewer 
gases  are  never  so  bad  as  when  emitted 
from  sewage  spread  out  upon  the  land. 
This  statement  is  worthy  of  considera- 
tion. Solid  matter  is  given  off  during 
evaporation.  As  the  turpentine  in  lead 
paint  is  evaporating,  solid  lead  carbonate 
is  carried  into  the  air,  and  produces 
lead  poisoning  amongst  the  inmates  of 
the  freshly  painted  house.  This  cannot 
result  from  any  volatility  of  the  lead, 
but  merely  from  the  mechanical  dis- 
lodgment  of  lead  particles  during  the 
evaporation  of  the  volatile  constituents 


96 


of  the  paint.  For  when  the  smell  has 
gone,  the  danger  has  passed.  The  sanit- 
arian recognizes  the  importance  of  defe- 
cating the  excreta  of  the  typhoid  patient 
as  soon  as  evacuated,  and  of  removing  it 
from  the  sick  room  without  delay.  And 
why  I  To  prevent  the  materies  morbi 
being  carried  into  the  air  during  the 
evaporation  of  the  liquid  portion.  It 
must,  therefore,  be  an  unscientific  meth- 
od to  spread  the  sewage  of  a  mixed 
population  over  the  land,  thereby  in- 
creasing the  area  of  evaporation.  Mr. 
Hawksley's  words  may  be  quoted  here. 
They  are  the  record  of  one  whose  unique 
experience  is  only  rivaled  by  his  acute 
powers  of  observation  :  "  Water  irriga- 
tion carried  on  in  warm  weather  is  ex- 
ceedingly unhealthy.  I  can  speak  posi- 
tively to  it  from  repeated  observation  in 
different  places,  that  the  odor,  particu- 
larly at  night  and  particularly  upon  still 
damp  evenings  in  autumn,  is  very  sickly 
indeed,  and  that  in  all  these  cases  a  great 
deal  of  disease  prevails.  The  sewage 
forms  a  deposit  on  the  surface  of  the 


97 

ground,  that  deposit  forms  a  cake  of 
organic  matter,  and  organic  matter  when 
it  is  in  a  damp  state,  as  it  usually  is, 
gives  off  in  warm  weather  a  most  odious 
stench." 

There  is  yet  another  point  to  be  con- 
sidered. That  a  district  saturated  with 
moisture,  and  more  particularly  if  along 
with  the  moisture  there  is  an  excess  of 
organic  matter  (I  am  excluding  specific 
morbid  emanations),  is  unhealthy  and 
malarious,  the  fens  of  Lincolnshire  and 
the  rice  fields  of  China,  not  to  speak  of 
other  places,  supply  abundant  evidence. 
Buchanan,  in  a  masterly  research,  has 
shown  that  phthisis  is  more  prevalent 
where  there  is  a  wet  atmosphere  than 
where  there  is  a  dry  one,  whilst  Petten- 
kofer,  of  Munich,  regards  fever  and 
cholera  as  dependent  on  fluctuations  in 
the  level  of  ground  water  charged  with 
sewage.  The  case  is  serious.  Saturate — 
be  continually  saturating — a  large  area 
with  sewage  water,  and  as  a  consequence 
be  continually  raising  the  subsoil  water, 
an  increased  humidity  of  atmosphere 


98 


must  result,  and  conditions  favorable  to 
malaria,  fever,  and  phthisis. 

Dr.  Sturge,  in  1879,  in  a  paper  before 
the  Institution  of  Surveyors,  gave  some 
important  details  respecting  the  sewage 
of  Paris.  70  per  cent,  of  the  Parisian 
houses  have  cesspools,  but  even  of  the 
remaining  30  per  cent.,  the  solid  excre- 
ment is  not  allowed  to  enter  the  sewers. 
Some  analyses  of  Paris  sewage  were 
given  (respecting  which,  however,  I  speak 
with  caution)  showing  56  grains  of  or- 
ganic, and  123  grains  of  inorganic  mat- 
ter per  gallon. 

Of  the  total  60,000,000  gallons  daily 
of  Paris  sewage,  10,000,000  are  treated 
on  914  acres  of  land  at  Gennevilliers. 
This  land  has  about  five  inches  of  al- 
luvial soil  resting  on  ten  feet  of  sand  and 
gravel.  I  omit  all  reference  to  the  agri- 
cultural success  or  non-succ*ess  of  the 
Gennevilliers  farm,  but  it  must  be  noted 
that  authorities  consider  that  the  value 
of  building  land  in  the  neighborhood 
has  decreased,  and  the  health  of  the  in- 
habitants suffered  from  a  rise  in  the 


99 

level  of  the  subsoil  water.  I  quote  Dr. 
Sturge's  words  (p.  153) :  "  Great  com- 
plaints have  been  made  that  since  the  in- 
troduction of  the  irrigation,  ague  has 
become  far  more  common  than  it  was 
before,  and  more  deaths  occur  from 
diarrhoea  and  dysentery." 

One  thing  is  abundantly  evident,  even 
to  any  untrained  observer,  viz.,  that  it  is 
impossible  to  insure  a  pure  effluent  by  an 
irrigation  process.  The  land  which  is 
covered  with  an  active  crop  of  vigorous 
vegetation,  is  a  totally  different  purify- 
ing area  from  the  same  land  upon  which 
no  rye  grass  or  other  vegetation  is  grow- 
ing. The  land  under  the  influence  of 
summer  warmth  and  active  evaporation 
is  entirely  different  from  what  it  is  at 
times  of  frost  or  snow.  The  land  flooded 
with  heavy  rain^  is  different  land  from 
what  it  is  in  dry  weather.  Inequality  of 
purification,  uncertainty  of  action— at 
one  time  good,  at  another  doubtful,  at 
another  absolutely  useless — is  the  record 
I  have  to  give  from  personal  observa- 
tion, and  that  on  no  limited  scale,  of  ir- 


100 

rigation  as  a  method  of  purifying  sew- 
age. The  sewage  comes  every  day  to  be 
treated,  and  no  earthly  power  can  say 
whether  your  farm  is  or  will  be  in  a  con- 
dition to  deal  with  it.  And  more  than 
this — the  very  condition  that  increases 
the  quantity  of  the  sewage  to  be  dealt 
with  (such  as  heavy  rain),  is  the  very 
condition  that  renders  your  land  tem- 
porarily disabled.  And  yet  further  still, 
the  very  condition  that  increases  the 
bulk  of  your  sewage,  or  at  any  rate  its 
polluting  character — the  population — is 
that  condition  which  renders  costly  the 
land  in  the  neighborhood,  and  probably 
makes  it  altogether  impossible  to  pro- 
cure at  any  price.  I  give  on  p.  1151 
certain  analyses  of  sewage  effluents  from 
different  farms. 

II.— POLLUTION   OF   SUBSOIL  WATEK,  AND 
OF  KUNNING  STKEAMS. 

The  select  committee  on  the  sewage  of 
towns,  although  champions  of  irrigation, 
admit  that  if  the  power  of  the  soil  be 
overtaxed  (that  is  if  too  much  sewage 


101 

be  applied)  there  must  of  necessity  be 
injury  to  wells  and  running  streams. 

III. — DISTRIBUTION  OF  UNDEFECATED  SEW- 
AGE CONTAINING  THE  OvA  OF  ENTOZOA. 

The  fact  has  always  been  recognized 
that  entozoic  diseases  have  an  external 
origin — L  e.,  that  the  ova  or  parasites 
come  from  without,  and  are  not  gene- 
rated within,  the  human  body.  Millions 
of  ova  are  voided  with  every  segment 
discharged  by  the  person  afflicted  with 
tapeworm,  each  ovum  being  capable  of 
producing  a  measle  in  the  flesh  of  an 
animal,  and  each  measle  a  tapeworm  in 
the  body  of  the  man. 

Here,  then,  are  two  serious  conse- 
quences of  irrigation  worth  considering : 

I  have  seen  watercresses  and  celery 
grown  OD  sewage  ground,  having  a  quan- 
tity of  dried  sewage  matter  deposited  on 
the  stems.  I  have,  with  more  than  a 
cook's  patience,  tried  to  wash  this  mat- 
ter off,  but  the  tenacity  with  which  it 
sticks  upon  the  surface  of  the  vegetable 
when  once  dry  is  perfectly  astounding. 


102 

Be  it  remembered  that  watercresses 
celery  are  eaten  uncooked.  I  have  seen 
cabbages  and  turnips,  not  merely  grown 
on  sewage  ground,  but  carefully  pre- 
pared arrangements  made  for  a  weekly 
flooding  with  sewage,  the  market  produce 
being  placed  in  a  kind  of  reservoir  per- 
mitting sufficient  raw  sewage  to  flow  into 
it,  so  that  it  may  completely  cover  the 
vegetation. 

The  grass  covered  with  sewage,  eaten, 
as  it  is  with  rapacity  by  the  cattle,  infect 
their  bodies  with  the  larval  parasite. 
Thus  the  meat  is  measly,  and  measly 
meat,  except  for  efficient  cooking,  means 
tapeworm  to  the  human  subject.  Per- 
haps a  similar  story  might  be  told  of 
trichina,  with  its  ten  times  greater  dan- 
ger. No  doubt,  as  an  accident,  the  dan- 
ger is  constant,  but  sewage  irrigation 
would  practically  render  it  an  affair  of 
certainty.  In  other  words,  sewage  al- 
ways contains  excre mental  ova.  The 
farm,  therefore,  that  receives  sewage 
must  be  more  liable  to  produce  measly 
meat  than  the  farm  that  does  not  receive 
it. 


103 

"  May  we  not,  indeed,"  says  Dr.  Cob- 
bold,  "  but  too  reasonably  conjecture 
that  the  wholesale  distribution  of  tape- 
worm eggs,  by  the  utilization  of  sewage 
on  a  stupendous  scale,  will  tend  to 
spread  abroad  a  class  of  diseases  some 
of  which  are  severely  formidable?  So 
convinced  am  I  of  the  truth  embodied  in 
an  affirmative  reply  to  this  latter  query, 
so  certain  am  I  that  parasites  are  propa- 
gated in  this  particular  way,  so  surely  do 
I  see  unpleasant  results  if  no  steps  are 
taken  to  counteract  the  evil,  that  I  feel 
myself  bound  to  speak  out  boldly,  and 
to  produce  no  uncertain  sound  in  the 
matter,  which  most  closely  concerns  hu- 
manity. The  whole  question  is,  in  truth, 
of  vast  hygienic  importance." 

Let  us  review  our  facts.  We  have 
dilute  sewage  to  deal  with.  We  desire 
to  be  sanitarians,  viz.,  to  purify  our  sew- 
age so  that  it  shall  not  pollute  our 
watercourses,  nor  cause  nuisance.  We 
desire  to  be  economists,  viz.,  to  get  out 
of  the  sewage  all  that  is  valuable  in  it, 
In  a  word,  we  desire  to  achieve,  by  one 


104 

and  the  same  operation,  a  sanitary  suc- 
cess and  a  commercial  profit  In  sewage 
treatment,  as  in  other  things,  you  cannot 
combine  the  impossible.  Achieve  your 
commercial  success,  and  you  must 
abandon  sanitary  considerations.  You 
must,  as  at  Edinburgh,  flood  your  land 
with  your  thousands  of  tons  of  sewage 
per  acre,  until  your  farm  is  a  stinking 
morass,  and  your  effluent  water  so  im- 
pure that  you  must  take  it  directly  into 
the  sea  lest  you  foul  your  watercourses. 
Achieve  your  sanitary  success,  sprinkle 
your  300  tons  per  acre  per  annum  on 
your  land  with  hose  and  jet,  and  away 
goes  your  agricultural  profit.  Try  a 
compromise  between  the  extremes  of  the 
300  and  10,000,  and  you  get  the  diffi- 
culties of  both  with  the  advantages  of 
neither.  I  admit  possible  exceptions  :  a 
small  population ;  cheap  land  removed 
from  human  habitation ;  a  porous  soil 
admitting  free  percolation ;  happy  gradi- 
ents not  requiring  steam  power;  prox- 
imity to  the  sea,  so  that  extreme  purity 
of  effluent  need  not  be  demanded  ;  prox- 


105 

imity  to  a  town,  so  that  a  ready  sale  for 
the  sewage  grass  for  dairy  purposes  can 
be  secured.  But  the  difficulties  are 
enormous.  I  must  have  enough  land — 
and  the  greater  the  population  with 
whose  sewage  I  have  to  deal,  the  greater 
the  quantity  of  land  required,  and  the 
larger  probably  its  price.  I  must  have 
proper  land — sufficiently  porous,  but  not 
too  porous,  properly  leveled  and  drained. 
If  the  level  of  my  land  be  above  the 
sewer  outfall,  I  require  costly  motive 
power.  The  larger  the  quantity  of  sew- 
age (as  in  wet  weather)  with  which  I 
have  to  deal,  the  less  able  is  the  already 
over-loaded  ground  to  cope  with  it. 
Frost  or  snow,  the  work  has  still  to  be 
done.  At  all  times  the  effluent  must  be 
sufficiently  pure,  lest  litigants  be  aroused. 
At  all  times  the  operations  must  be  con- 
ducted without  offensive  smells  from  an 
over- sodden  state  of  soil,  and  without 
polluting  the  air  by  rendering  it  ab- 
normally damp  or  polluted  by  sewage 
effluvia,  the  prolific  source  of  typhoid. 
The  subsoil  water  must  be  so  diverted, 


106 

that  neighboring  wells  shall  not  be  pol- 
luted. Grant  all  these  difficulties  over- 
come, and  there  remains  as  the  produce 
of  my  farm  a  grass  only  fit  for  dairy  pur- 
poses, and  even  then  likely  to  be  a 
source  of  entozoic  infection  to  man  and 
animals. 

STRAINING,  FILTRATION,  AND  SUBSIDENCE. 

Many  attempts  have  been  made  not 
only  to  strain  and  filter  sewage,  but  also 
to  allow  the  deposition  of  the  larger 
pieces  of  the  suspended  matters  in 
tanks,  with  or  without  straining.  As  a 
fact,  it  is  impossible  to  strain  sewage  effi- 
ciently, or  to  effect  deposition  without 
previous  treatment.  If  the  straining 
material  be  of  fine  texture,  such  as  of 
wire,  it  soon  clogs,  whilst  if  it  be  of 
coarse  texture,  it  is  of  no  use.  If  fine 
gauze,  or  an  iron  grate  be  used,  the 
albuminous  matters  soon  choke  it,  and 
prevent  further  action.  In  Baldwin 
Latham's  self-cleansing  extractor  (an  in- 
genious contrivance  in  use  at  Dantzic, 
Croydon^Coventry,  etc.),  and  consisting 


107 

of  a  vertical  strainer  rotating  about  a 
horizontal  axis,  the  solid  matter  being 
raised  from  a  central  receptacle  by  an 
Archimedean  screw,  the  most  that  can 
be  said  is  that  the  grosser  matters  are 
removed.  But  even  here,  a  considerable 
play  of  water  upon  the  gauze  is  required 
to  ensure  its  action.  It  was  formerly  a 
common  practice  to  strain  the  sewage 
through  wooden  planks  perforated  with 
f-inch  apertures,  before  applying  it  to 
land,  a  proceeding  that  reduced  the  sus- 
pended matters  some  9  or  10  per  cent. 

A  combined  system  of  subsidence  and 
filtration  has  been  attempted  on  many 
occasions.  This  method  was  formerly 
adopted  at  Birmingham,  where  the  sewage 
was  conveyed  through  a  series  of  tanks, 
the  passage  occupying  about  two  hours. 
Two  sets  of  tanks  were  employed,  each 
set  being  worked  continuously  for  about 
a  fortnight,  when  the  sludge  was  re- 
moved and  consolidated  by  evaporation 
and  soakage  in  properly  prepared  pits. 
The  effluent  water  was  found  to  be 
offensive,  and  the  works  a  nuisance. 


108 

Coventry  formerly  adopted  a  similar 
process,  a  coarse  gravel  filter  running  the 
whole  length  of  one  tank  being  employed, 
through  which  it  passed  into  a  second, 
and  again  into  a  third  tank  of  small 
gravel.  The  purification  proved  very 
inefficient. 

At  St.  Thomas,  adjoining  Exeter,  a 
similar  method  of  defecation  by  subsiding 
ranks,  iron  strainers,  and  gravel  filters 
(forming  the  tank  boundaries)  was 
adopted,  although  in  this  case  a  little 
lime  and  about  0.75  gallon  of  carbolic 
acid  to  200,000  gallons  of  sewage  were 
added.  The  carbolic  acid  proved  valu- 
able. 

At  Uxbridge  again,  a  combined  system 
of  subsidence,  straining  through  a  grat- 
ing, and  filtration  through  charcoal,  is 
adopted,  before  the  sewage  is  discharged 
into  the  Colne.  It  is,  however,  quite 
certain  that  mere  subsidence  and  filtra- 
tion, as  methods  of  sewage  treatment, 
are  failures. 

We  may  here  mention  the  suggestion 
of  Strang,  of  Glasgow,  of  treating  the 


109 

sewage  discharged  from  a  water  closet, 
by  upward  filtration  through  a  box  con- 
taining the  refuse  ashes  of  the  house. 
By  this  means  the  solid  matter  is  re- 
tained in  the  lower  part  of  the  vessel, 
and  the  liquid  matter  passes  through  the 
ashes.  Dr.  Anderson,  of  Glasgow,  re- 
ports well  of  the  apparatus.  Mr.  Austin, 
late  of  the  Local  Government  Board 
Office,  was  of  opinion  that  sewage  might 
be  dealt  with  by  placing  a  series  of 
portable  filters  in  the  sewers.  (Society 
of  Arts  Conference,  1877,  p.  14.)  By 
this  means  much  of  the  kitchen  stuff 
could  be  kept  out  of  the  sewers,  which, 
it  is  true,  is  often  as  objectionable  as,  if 
not  more  objectionable  than,  the  sewage 
itself. 

Whatever  filtering  material  you  use,  be 
it  sand,  gravel  or  charcoal,  two  difficul- 
ties are  inevitable : — (1)  That  the  filter 
soon  becomes  choked,  when  it  fails  to 
act,  or  acts  inefficiently ;  (2)  that  the  mat- 
ters deposited  on  the  surface  of  the'filter 
cause  an  insufferable  nuisance.  It  may 
be  said,  as  regards  the  first  objection, 


110 

you  have  only  to  recharge  your  filters 
and  to  utilize  the  old  material  for  manure. 
The  answer  is,  the  cost  of  material  and 
of  labor,  and  the  difficulty  of  securing  a 
sale  for  your  refuse.  To  meet  the 
second  objection  it  is  said,  "  Cultivate 
the  surface  of  your  filter  beds,  whereby 
vegetation  can  be  made  to  use  up  the 
obnoxious  matters."  In  practice,  how- 
ever, this  is  not  successful,  whilst  it  is 
impossible  to  secure  a  crop  all  the  year 
round. 

I  know  of  no  place  where  filtration 
alone  has  proved  a  success  hygienically. 
Of  course  intermittent  downward  filtra- 
tion is  practically  land  filtration.  The 
objections  urged  to  general  filtration 
apply  equally  to  land  filtration. 

Some  interesting  details  respecting  the 
filtration  of  the  foul  water  of  the  River 
Plate  is  given  by  Mr.  George  Higgin 
("Proc.  Inst.  Civil  Engineers,"  vol.  Ivii.) 
They  show  the  extreme  difficulty  of  filter- 
ing this  impure  water,  a  difficulty  which 
is  nothing  compared  to  that  of  filtering 
sewage. 


Ill 

DISCHARGE  OF  SEWAGE  INTO  THE  SEA. 

Seeing  sewage  is  worth  so  little,  it  is  no 
wonder  that  local  authorities  have  been 
desirous,  where  possible,  to  get  rid  of 
it  by  permitting  its  discharge  into  the 
sea  (see  Hawksley's  Social  Science  Ad- 
dress 1876,  p.  28).  This  has  been  done 
at  Weston-Super-Mare,  St.  Leonards, 
Torquay,  Eastbourne,  Llandudno,  Dover, 
Carnarvon,  Brighton,  Margate,  and  Rams- 
gate.  There  is  much  to  be  said  in  favor 
of  this  method.  No  doubt  it  appears 
wasteful,  but  nature  is  certain  to  utilize 
in  due  course  in  her  own  way  what  we 
fail  to  utilize  in  ours.  But  it  must  be 
noted  that  a  nuisance  is  possible  if  the 
sewage  be  discharged  into  the  sea  too 
near  land,  from  the  foul  matters  in  sus- 
pension being  brought  back  again  b}rthe 
tide  to  putrefy  on  the  shore  during  low 
water.  This  was  said  to  have  occurred 
at  Dover  ("Proc.  Inst.  Civil  Engineers," 
vol.  xliii.  p.  221)  and  at  Carnarvon.  A 
stink  may  result,  moreover,  from  the  re- 
duction of  the  sulphates  of  sea  water  to 
sulphides  by  the  organic  matter  in  the 


112 

sewage,  and  the  evolution  of  sulphuretted 
hydrogen  by  the  action  of  carbonic  acid 
on  the  sulphides  so  formed.  Possibly 
to  some  such  cause  the  smells  and  un- 
sanitary condition  of  the  Bay  of  Naples, 
the  Port  of  Marseilles,  the  Bay  of  Cadiz, 
the  West  Coast  of  Africa,  and  other 
places  owe  their  origin.  This  difficulty 
is  worth  considering,  moreover,  more 
particularly  in  those  cases  where  a  town 
extends  down  to  the  water's  edge.  No 
doubt  further  sewage  matters,  flocculent 
materials,  corks,  etc.,  have  a  special  ten- 
dency to  float  on  sea  water,  continuous 
decomposition  resulting.  Difficulties  have 
arisen  at  Margate,  Eamsgate,  and  Brigh- 
ton, from  these  several  causes. 

Evils  resulting  from  the  discharge  of 
sewage  into  tidal  rivers  containing  sea 
water  have  occurred  at  Glasgow  and 
towns  adjacent,  where  the  sewage  was 
taken  into  the  Clyde,  and  were  investi- 
gated by  Sir  John  Hawkshaw  in  1874, 
who  recommended  its  discharge  into  the 
Firth  of  Clyde  at  Farland  Head.  The 
discharge  of  sewage  into  the  Thames  was 


113 

also  a  subject  of  inquiry  b$  a  Royal  Com- 
mission, and  was  discussed  by  Professor 
Stanley  Jevons  in  a  letter  to  the  Times 
of  December  2,  1878.  I  need  only  point 
out  that  the  discharge  of  sewage  into  a 
tidal  river  involves  cost  for  dredging. 

Regarding  sewage  (which  I  do)  as  a 
thing  to  be  got  rid  of,  and  for  which  we 
must  be  prepared  to  pay  to  be  rid  of  it, 
there  are  manifest  advantages  in  taking  it 
out  to  sea  or  estuary.  It  should,  how- 
ever, in  such  cases,  be  discharged  in  deep 
water,  at  a  considerable  distance  from 
land  below  the  line  of  low  water,  and 
where  there  is  a  well-ascertained  current 
to  carry  it  permanently  seaward.  Careful 
tidal  observations  are  needed  before  de- 
ciding on  the  point  of  discharge.  A  spot 
where  there  is  an  oscillating  action  re- 
sulting in  a  return  of  sewage  matter, 
either  in  the  neighborhood  of  the  dis- 
charge, or  at  distant  places  to  which  the 
tide  carries  it,  must  be  avoided — in  other 
words,  we  must  not  allow  a  turn  of  the 
tide  to  carry  one  person's  refuse  to  some- 
body else.  It  is  difficult  to  imagine  a 


114 

nuisance  resulting  under  carefully  con- 
sidered conditions,  more  particularly  if 
the  discharge  pipe  be  some  distance  from 
the  town,  and  the  town  itself  well  above 
the  sea  level.  Still,  even  in  all  cases,  it 
is  worth  considering  whether  or  not 
some  process  of  clarification  may  not  be 
advisable. 

It  is  worthy  of  note  that  chloride  of 
magnesium  is  itself  a  precipitating  agent 
for  sewage.  Again,  sea  water,  owing  to 
the  common  salt  present  in  it,  has  a  ten- 
dency to  reduce  the  ease  with  which  or- 
ganic matter  is  oxidized.  Thus  the 
oxidation  of  the  organic  impurity  of  the 
sewage  is  less  rapid  when  it  is  discharged 
into  salt  water,  than  it  is  when  discharged 
into  fresh. 

In  the  "  mud  inquiry,"  the  Conserva- 
tors of  the  Thames  contended  that  cer- 
tain sewage  banks  in  the  river  were  caused 
by  the  sewage  outfalls  at  Barking  and 
Crossness.  In  time,  these  sewage  depos- 
its putrefy,  rise  to  the  surface,  give  off 
offensive  gases,  ultimately  sinking  to  un- 
dergo fresh  putrefactive  changes.  It  is 


115 

certain  that  in  a  tidal  salt  river,  foul 
banks  of  sewage  mud  may  form,  which 
in  ordinary  rivers  would  not  be  produced. 
Of  course,  I  admit  that  a  strong  tidal 
current  might  carry  these  masses  away, 
but  in  the  absence  of  such  current,  the}7 
subside  and  mingle  with  the  sand  and 
mud  of  the  beach. 


PRECIPITATION     PROCESSES. 

By  "  chemical  precipitation,"  or  "  the 
chemical  treatment  of  sewage,"  is  im- 
plied the  addition  of  certain  chemicals 
to  the  sewage,  whereby  the  deposition  of 
the  solid  suspended  matters  and  some 
of  the  dissolved  matter  from  the  forma- 
tion of  insoluble  compounds,  together 
with  the  deodorization  of  the  offensive 
constituents  precipitated  or  dissolved,  is 
effected.  The  general  features  of  a  chem- 
ical process  for  sewage  may  be  thus  de- 
scribed : 

To  the  sewage  (from  which  the  grosser 
suspended  matters  may  or  may  not  be 
removed)  chemicals  are  added,  either  sus- 


116 

pended  in  water,  or,  if  soluble,  dissolved 
in  water.  After  this  treatment,  the  sew- 
age^is  allowed  to  flow  into  subsidence 
tanks,  where  either  it  is  allowed  perfect 
rest'for  a  few  hours  or  is  passed  through 
a  series  of  tanks  continuously,  in  order 
in  either  case  to  allow  the  deposition  of 
the  sludge  — that  is,  of  the  matters  in 
suspension.  The  clear  effluent  is  then 
allowed^to  flow  either  directly  into  a 
watercourse,  or  over  land,  previously  to 
its*discharge.  The  black  fluid  or  sludge 
in  the  tank  (of  which  90  per  cent,  is  water) 
is  then  all  that  remains  to  be  dealt  with. 
The  precipitants  to  be  employed  have 
been  subject  matters  of  numerous  patents. 
Of  these  we  shall  note  the  most  import- 
ant. 

I. — PROCESSES  INVOLVING  THE  USE  OF  LIME 
AS 'THE  CHIEF  PRECIPITATING  AGENT. 

Lime. — The  use  of  lime  for  disinfect- 
ing excreta  was  the  subject  of  a  patent 
in  1802  (Estienne).  In  1844  lime  was 
used  to  purify  the  Manchester  sewage 
before  discharge  into  the  River  Medlock. 


117 

This  was  done  at  the  suggestion  of  Dr. 
Clark,  of  Aberdeen,  who  at  that  time  was 
at  work  at  his  process  for  softening  wa- 
ter by  the  use  of  lime,  and  as  the  result 
of  which,  he  was  led  to  suggest  its  use 
for  sewage  precipitation.  It  was  aban- 
doned for  a  time  at  Manchester  on  the 
ground  of  cost  (a  ton  of  lime  being  re- 
quired daily),  but  was  re-adopted  in  1854, 
at  the  suggestion  of  Grace  Calvert,  who 
advised,  after  the  addition  of  two  or 
three  grains  of  lime  per  gallon,  complete 
rest  of  the  liquid  so  treated  in  subsidence 
tanks,  his  report  stating  that  the  pre- 
cipitate subsides  rapidly,  the  supernatant 
water  being  clear,  colorless,  and  inoffens- 
ive. 

In  1846,  Mr.  William  Higgs  took  out 
his  patent  for  the  treatment  of  sewage  in 
subsiding  tanks  or  reservoirs  by  means 
of  chemical  agents.  For  the  purpose  of 
precipitating  the  solid  animal  and  vege- 
table masters  contained  therein,  hydrate 
of  lime  (commonly  termed  slack  lime) 
was  preferred.  In  1851,  Mr.  Thomas 
\Vicksteed  patented  a  process  for  manu- 


118 

facturing  manure  from  sewage,  etc.,  by 
admixture  with  lime,  collecting  the  de- 
posit and  submitting  it  to  certain  centri- 
fugal drying  machinery,  thus  obtaining, 
to  use  his  own  words,  "  the  manure  as 
fertilizing  material  in  a  state  commodi- 
ous for  transport." 

Action  of  Lime. — When  lime  is  added 
to  raw  sewage,  a  carbonate  of  lime  is 
first  formed.  This  acts  as  a  weighting 
material,  whereby,  if  the  opportunity  be 
afforded,  the  light  flocculent  suspended 
matters  will  be  carried  down  along  with 
the  precipitated  carbonate.  In  addition 
to  this,  however,  a  certain  proportion  of 
dissolved  organic  matter  is  also  precipi- 
tated, the  lime  forming  with  the  organic 
matter  a  compound  of  uncertain  chemical 
composition. 

Grace  Calvert,  operating  on  the  Man- 
chester sewage,  gives  the  following  as 
the  average  results  of  five  days'  treat- 
ment by  lime : 

/ Matters  in  Solution. , 

Total  solids.         Mineral.          Organic. 

Raw  sewage..  32.00     ..     23.46     ..       8.54 
Effluent..       .  25.76  22.26  3.50 


119 

, Matters  in  Suspension. » 

Total  solids.         Mineral.          Organic. 

Raw  sewage..     6.65     ..       3.08     ..       3.57 
Effluent 0..  0..  0 

The  action  of  lime  on  London  sewage 
was  the  subject  of  a  prolonged  investiga- 
tion by  Dr.  Letheby  during  the  time  I 
acted  as  his  assistant. 

In  Calvert's  experiments  on  Manchester 
sewage  the  lime  effected  the  entire  re- 
moval of  the  suspended  matter  (mineral 
and  organic),  and  more  than  50  per  cent, 
of  the  dissolved  organic  matter.  In 
Letheby's  and  my  own  experiments,  the 
removal  of  all  the  suspended  matter  was 
effected,  and  about  one-fourth  of  the  dis- 
solved organic  matter. 

The  action  of  lime  was  further  investi- 
gated and  reported  on  by  Hofmann  and 
Witt,  as  one  of  the  most  promising  of 
the  many  processes  for  obtaining  a  de- 
posit from  sewage,  which,  when  dry, 
might  be  employed  as  manure.  Opera- 
ting on  London  sewage  with  20  grains 
of  lime  per  gallon  (800  grains  of  lime  to 
40  gallons  of  sewage),  the  following  re- 
sults were  obtained : 


120 

, Matters  in  Solution. . 

Total  solids.         Organic.          Mineral. 

Raw  sewage . .  107 . 6       . .     52 . 36     . .     55 .24 
Effluent 96.02     ..     40.34     ..     55.68 

t Matters  in  Suspension. ^ 

Total  solids.         Organic.         Mineral. 

Raw  sewage..  52.49     ..     36.4     ..       16.09 
Effluent  . .      . .  traces.   . .  traces.   . .      traces. 

In  other  words,  20  grains  of  lime  re- 
moved all  the  suspended  matter,  and 
more  than  one-fourth  the  dissolved  or- 
ganic matter. 

After  the  addition  of  the  lime  a  floccu- 
lent  precipitate  is  formed.  This  settles 
at  the  rate  of  about  one-fourth  part  the 
bulk  of  the  liquid  in  one  hour.  The 
clear  supernatant  liquor  is  colorless, 
clean,  and  comparatively  odorless.  Hy- 
gienically,  the  process  is  successful — com- 
mercially, it  is  not  successful,  because 
the  precipitate  is  mainly  carbonate  of 
lime  and  non-nitrogenous  organic  matter. 

These  laboratory  experiments  are  con- 
firmed by  practical  working.  Thus 
Higgs'  process  was  used  at  Tottenham 
in  1857,  the  results  being  so  satisfactory 
that  the  Local  Board  of  Health  gave  a 


121 

testimonial  certifying  to  its  efficiency 
(sewage  treated  175,000  gallons  daily,  or 
sewage  of  10,000  persons — 12  grains  of 
lime  added  per  gallon  (1  ton  per  week) 
— dry  precipitate  obtained  was  four  to 
five  times  the  weight  of  the  lime  used). 
That  the  success  was  no  mere  accident 
is  proved  by  the  high  eulogium  passed 
on  the  process  by  Normandy  and  Miller 
in  the  action  brought  by  Higgs  against 
the  Hitchin  Local  Board  for  an  infringe- 
ment of  his  patent. 

Why,  then,  was  not  this  hygienic  suc- 
cess continued?  The  reason  is  obvious-the 

TOTTENHAM. 


-Matters  in  Solution.  - 


Total  solids.  Organic.  Mineral.Am'onia. 
Raw  sewage.  54.50  ..  9.49  ..  45.01  ..  2.60 
Effluent 48.99  ..  8.01  ..  45.98  ..  2.84 

Matters  in  Suspension. . 

Total  solids.         Organic.          Mineral. 

Raw  sewage..  39.99     ..     14.53     ..     25.46 
Effluent 1.69     ..       0.37     ..       1.32 

manure  was  found  to  be  of  so  little  value 
that  the  commercial  result  proved  a  fail- 
ure, Mr.  Higgs  transferred  his  expensive 


122 

works  for  a  merely  nominal  sum  to  the 
local  authority,  who  (in  spite  of  their 
testimonial  showing  the  capabilities  of 
the  process)  so  neglected  them,  that 
shortly  after  the  transference,  an  injunc- 
tion was  obtained  by  the  trustees  of  the 
River  Lea,  to  prevent  foul  undefecated 
sewage  being  discharged  from  the  works. 
Carelessness  and  parsimony  are  certain 
to  ruin  the  best  of  processes. 

WicksteecTs  process  was  adopted  at 
Leicester  in  1855,  the  works,  which  cost 
£30,000  to  £40,000,  being  managed  in 
the  first  instance  with  marked  success. 
[Sewage  treated  (1858),  2,000,000  gallons 
daily,  or  the  sewage  of  65,000  persons,  3 
to  16  grains  of  lime  were  added  per  gal- 
lon. Sludge  (dry)  was  3  to  4  times  the 
weight  of  the  lime  used.] 

Very  high  was  the  commendation  pass- 
ed on  this  process  by  Aitkin  and  Taylor, 
after  a  minute  investigation  in  1851. 
But  the  Corporation  shirked  the  lime, 
and  neglected  the  works.  No  wonder 
that  the  River  Soar,  into  which  the  efflu- 
ent is  discharged,  became  foul,  a  result 


123 

LEICESTER. 

Constituents  , — Matters  in  Solution. — 

per  gallon.  Total  solids.  Organic.  Mineral.Am'onia. 
Raw  sewage. 70. 00  ..  13.49  ..  56.51  ..  2.52 
Effluent 66.99  ..  10.65  ..  56.34  ..  2.61 

Constituents  , Matters  in  Suspension. » 

per  gallon.    Total  solids.  Organic.         Mineral. 

Raw  sewage..  19.15     ..  5.50     ..     1365 

Effluent 1.40     ..  0.49     ..       0.91 

which  is  certain  to  be  attributed  by  par- 
tisans to  failure  of  the  lime  process  ra- 
ther than  to  its  true  cause,  viz.,  the  mis- 
erable carelessness  and  false  economy  of 
those  to  whom  the  management  was  en- 
trusted. 

The  value  of  the  sludge  precipitated 
by  lime  has  been  variously  estimated  as 
from  15s.  6d.  to  29s.  6d.  per  ton. 
Voelcker,  who  fixed  15s.  5d.,  gives  the 

following  as  its  composition  : 

Value  per  ton. 

Moisture 10.52 

Organic  matter 12.46        . .         £1 

Phosphate  of  lime.     2.*7         ..          7 
Mineral  matter. ...  54 . 75  — 


100.00 

Nitrogen 0.60 

Ammonia 0.72  56 


124 

No  doubt,  as  an  agricultural  article^ 
this  manure  is  worth  very  little  indeed 
compared  to  the  extravagant  views  enter- 
tained of  its  fertilizing  power  by  the 
earlier  patentees.  Local  authorities  have 
to  learn  that  to  treat  sewage  means  out- 
lay, and  that  cost  is  no  excuse  for  neg- 
lect. 

I  conclude  by  laying  down  certain  es- 
sentials for  the  successful  treatment  of 
sewage  with  lime : 

1.  The  lime  used  should  be  in  a  per- 
fectly caustic  state,  and  before  admixture 
with   the   sewage   should  be  thoroughly 
slaked  and  mixed  with  sufficient  water  to 
render  it  the  consistency  of  a  thick  cream. 

2.  That  the  quantity  added  should  not 
be  less  than  ten  grains  per  gallon,  to  a 
sewage  that  does  not  exceed  thirty  gal- 
lons per  head  of  the  population. 

3.  That  very  complete  agitation  of  the 
lime  with  the  sewage  is  advisable  in  or- 
der to  secure   perfect  admixture  of  the 
lime  and  flocculation  of  the  precipitate, 
thus  rendering  the  after  subsidence  more 
rapid.     This   admixture  is   effected  pre- 


125 

ferably  by  means  of  a  paddle-wheel  mixer, 
the  axis  of  which  is  at  the  water  line  of 
the  well  in  which  the  mixing  process  is 
effected. 

4.  That  after  precipitation  the  defeca- 
ted  sewage  should  flow   over  an  apron 
into  a  tank,  which  should  be  at  least  4  ft. 
deep,  and  capable  of  holding  at  least  one 
hour's  sewage,  and  from  this  into  a  sec- 
ond tank  over  a  weir  placed  half  an  inch 
below  the  surface  and  at  the  opposite  end 
to   the   apron    over    which   the    sewage 
enters,  this  second  tank  being  capable  of 
holding  at  least  four  hours'  sewage. 

5.  Or,  if  this  continuous  process  be  not 
adopted,    the   defecated   sewage    should 
then  be  allowed  to  remain  at  rest  in  a 
tank  for  at  least  one  hour. 

6.  That  the  sludge  should  be  removed 
in   summer  time  once  in  48  hours,  and 
after   removal   be  pressed,  or  otherwise 
consolidated  and  dried  with  all  reason- 
able speed. 

The  frequent  removal  of  the  sludge  is 
a  matter  of  importance.  If  this  be  not 
done,  it  putrefies,  rises  in  large  flakes, 


126 

and  promotes  the  decomposition  of  the 
supernatanfwater.  It  is  not  difficult  by 
the  operation  of  a  dirty  tank  to  undo  all 
the  good  done  by  chemical  treatment. 
It  will  be  [manifest  that  a  double  set  of 
tanks  is  necessary/or  successful  working. 

LIME  AND  CHLORIDE  OF  LIME. 

At  Hertford,  in  1866,  about  8  J  bushels 
of  lime  and  150  Ibs.  of  chloride  of  lime 
were  used  daily  in  the  treatment  of 
1,640,000  gallons  of  sewage  per  day 
(=lime  2  grains,  chloride  of  lime  0.64 
grains  per  gallon).  At  this  time  the 
population  was  7,000,  showing  the  great 
quantity  of  subsoil  water  that  must  have 
mixed  with  the  sewage  in  its  transit  to 
the  works  (=  234  gallons  per  head). 
The  lime  (as  cream  of  lirne)  added,  was 
apportioned  to  the  rate  of  flow  by  little 
buckets  attached  to  a  water  wheel.  The 
treated  sewage  was  now  discharged  into 
a  depositing  tank.  The  tanks  are  in  du- 
plicate, each  tank  being  worked  three 
days,  where  it  remained  about  forty  min- 
utes, a  period  too  short  for  complete 


127 

subsidence.  The  tank  was  divided  under 
the  water  line  by  a  cross  wall,  the  sedi- 
ment being  thus  kept  back,  the  supernat- 
ant water  being  then  filtered  through  6 
or  7  inches  of  coarse  gravel  and  3  inches 
of  fine  sand.  The  filter  required  cleans- 
ing daily.  From  the  filter  beds  it  pass- 
ed into  an  effluent  channel  about  a  mile 
long,  to  be  discharged  into  the  Biver 
Lea  at  Ware  Mill.  About  12  cwt.  of 
sludge  was  removed  daily.  After  flowing 
along  the  outfall  channel  for  a  quarter 
of  a  mile,  it  became  clear,  fish  and  vege- 
tation being  found  in  the  water  in  abun- 
dance. 

In  1866    the  following  analyses  were 
obtained : 


128 


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129 

The  chloride  of  lime,  although  only 
one  third  of  a  grain  per  gallon,  not  only 
disinfected  the  sewage,  but  prevented  the 
growth  of  the  sewage  fungus. 

My  experience  enables  me  to  speak 
favorably  of  the  employment  of  chloride 
of  lime  with  lime,  especially  in  hot  wea- 
ther. About  56  Ibs.  per  1,000,000  gal- 
lons will  be  found,  as  a  rule,  fully 
sufficient  for  a  sewage  represented  by 
thirty  gallons  per  head  of  the  population. 

LIME  AND  SULPHATE  OF  SODA. 

Fuldds  Process.  This  process  was 
tried  on  a  small  scale  at  Pratt's  cloth 
mills  (Yeadon,  near  Leeds),  and  at 
Barnsley  Union  Workhouse  in  1873. 
The  process  was  abandoned,  the  effluent 
not  proving  satisfactory. 

SALTS  or  MAGNESIUM  WITH  TAR  AND  LIME. 

fritz  Hilles  Process. — The  process  of 
Fritz  Hille  (patented  1870)  was  to  be 
used  as  follows:  A  mixture  of  lime 
(100  Ibs.),  gas  tat-  (3  Ibs.),  chemical  salts, 
viz.,  chloride  of  magnesium  (17  lbs.),were 


130 

made  into  a  paste  with  180  Ibs.  of  water. 
Hille,  however,  does  not  bind  himself  to 
these  exact  quantities,  varying  them  ac- 
cording to  the  composition,  strength,  and 
quality  of  the  sewage  to  be  treated. 
From  the  decomposition  of  the  magne- 
sium chloride  by  the  lime,  a  bulky  pre- 
cipitate is  formed,  which  carries  down  the 
suspended  matter. 

The  exact  quantity  of  paste  to  be  added 
must  also  be  a  matter  of  experiment. 
It  will  vary  from  £  Ib.  to  1  Ib  per  100 
gallons,  or  from  10,000  Ibs.  (=4  tons,  9 
cwt.,  1  qr.,  4  Ibs.)  to  2,500  Ibs.  (=  1  ton, 
2  cwt.,  1  qr.,  8  Ibs.)  per  million  gallons. 
This  quantity,  however,  supposes  subse- 
quent nitration. 

Hille  suggests  that  the  sludge  may  be 
advantageously  used  again  as  a  precipi- 
tant for  fresh  sewage,  employing  for  this 
purpose  a  mixture  of  from  two  to  five 
parts  of  sludge  with  one  part  of  the  paste. 
Further,  he  considers  that  depositing 
tanks  are  not  essential,  but  that  the 
sewage  after  treatment  may  with  advan- 
tage be  applied  directly  to  the  land. 


131 

If  tanks  be  employed,  they  should  not 
be  used  for  more  than  three  days  at  a 
time. 

SALTS  OF  ALUMINA. 

Numberless  patents  have  been  taken 
out  for  treating  sewage  by  means  of 
compounds  of  alumina. 

If  sulphate  of  alumina  only  be  used, 
the  ammonia  of  the  sewage  would  in 
time  effect  its  decomposition,  resulting 
in  the  precipitation  of  alumina.  The 
action  of  alumina  thus  set  free  is  to  com- 
bine with  the  soluble  organic  matter, 
with  which  it  forms  an  insoluble  com- 
pound. Thus  it  is  used  as  a  mordant  or 
fixing  agent  for  colors  when  applied  to 
fabrics,  and  to  precipitate  coloring  mat- 
ters from  their  solutions,  forming  insolu- 
ble compounds  called  4klakes.''  Ammonia 
and  phosphoric  acid  are  also  fixed  by 
aluminous  compounds. 

titothert  (1852)  patented  a  mixture  of 
sulphate  of  alumina  (or  sulphate  of  zinc)r 
caustic  lime  and  charcoal  (obtained  from 
sewage  or  night  soil),  as  a  precipitant  for 


132 

sewage.  The  quantities  suggested  were 
73.5  grains  respectively  of  sulphate  of  al 
umina  and  charcoal,  3.5  grains  of  sulphate 
of  zinc,  and  22  grains  of  slaked  lime  per 
gallon.  The  lime  was  to  be  added  first, 
and  then  the  mixture  of  charcoal  with 
sulphate  of  alumina.  Hofmann  and  Witt 
report  (1857)  the  following  results  pro- 
duced with  5  ozs.  of  lime  and  10  ozs.  of 
the  alumina  mixture  to  40  gallons  of 
London  sewages 

. Matters  in  Solution. « 

Total  solids.         Organic.          Mineral. 

Raw  sewage..  107. 6       ..     52.36     ..     55.24 
Effluent..       .  87.73  37.56  50  17 


-Matters  in  Suspension.  - 


Total  solids.         Organic.          Mineral. 
Raw  sewage..  52.49     ..     36.4       ..     16.09 
Effluent none.     . .       — 

They  record  that  the  addition  of  the 
alumina  caused  a  marked  increase  of  sus- 
pended matter,  as  well  as  a  largely  in- 
creased flocculation  and  rapidity  of  sub- 
sidence. 

Stothert  claims  that  a  ton  of  the  ma- 
terials, costing  30s.,  will  make  two  tons 


133 

of  manure  worth  £2  2s.  per  ton,  contain- 
ing, when  dried,  1.44  per  cent,  of  am- 
monia, 8.6  per  cent,  of  phosphate  of  lime, 
and  34  per  cent,  of  organic  matter. 

I  do  not  know  of  this  process  having 
been  employed  on  a  large  scale. 

Lenk's  deodorizing  liquid  (patent,  1865), 
wasja  solution  of  alum  cake  (crude  sul- 
phate of  alumina)  containing  12  per  cent, 
of  alumina.  In  the  case  of  London  sew- 
age, 25  grs.  by  weight  of  the  solution 
sufficed  to  defecate  a  gallon  efficiently,  a 
very  flocculent  precipitate  forming,  which 
required  about  30  minutes  to  subside. 

This  process  \Yas  tried  at  Tottenham 
in  1858  for  about  one  week,  one  ton  of 
solution  (value  £6  10s.)  being  used  to 
treat  4,900,000  gallons  (700,000  daily). 
The  following  results  were  obtained  : 

( Matters  in  Solution. -p 

Phosphoric 
Total  solids.  Ammonia.  Organic,      acid. 

Raw  sewage.. 91. 10  ..  9.76  ..  42.30  ..  3.77 
Effluent 63.39  ..  4.23  ..  9.70  ..trace 

i Matters  in  Suspension. N 

Total  solids.         Organic.          Mineral. 

Raw  sewage.. 367. 7       ..225.6       ..142.1 
Effluent..  3.01  0.77  2.24 


134 

The  precipitation  was  very  successful. 
Voelcker  reported  that  "  the  effluent 
might  be  poured  into  any  watercourse 
without  causing  a  nuisance."  He  valued 
the  dry  deposit  at  from  25s.  to  30s.  per 
ton. 

A  curious  history  is  here  presented  of 
a  local  authority,  guardians  of  the  public 
health,  and  moreover,  under  an  injunc- 
tion not  to  pollute  the  Lea,  trying  a 
process  for  one  week,  which  they  admit- 
ted gave  "  fair  results,"  and  which  others 
know  to  have  been  more  than  fair,  and 
then  abandoning  it,  whether  from  care- 
lessness or  parsimony  I  do  not  know. 

Manning  (1853)  suggested  as  a  sew- 
age precipitant,  a  mixture  of  animal 
charcoal,  alum  carbonate  of  soda,  and 
gypsum,  some  caustic  lime  in  addition 
being  also  advised.  The  use  of  alum, 
on  account  of  its  expense,  was  afterwards 
dispensed  with  (patent,  1854),  by  the 
employment  of  a  waste  obtained  in  the 
course  of  the  alum  manufacture  from  the 
rough  liquors  (called  soft  sludge,  con- 
sisting of  sulphates  of  iron  and  alumina), 


135 

and  afterwards  (patent,  1855),  by  the  use 
of  various  aluminous  minerals  and  earths 
(alum  slate,  &c.),  treated  much  in  the 
same  way  as  that  adopted  in  the  prepara- 
tion of  alum. 

The  sewage  was  to  be  treated  as  fol- 
lows :  The  aluminous  preparation  wa's 
to  be  added  to  the  sewage,  and  the  whole 
agitated,  the  unslaked  lime  with  animal 
charcoal  being  introduced  during  the 
mixing.  The  treated  sewage  was  then 
to  be  allowed  to  subside  in  proper  tanks. 

This  process  was  favorably  spoken  of 
by  Penny,  of  Glascow,  who  gives  the  two 
following  analyses  of  the  sludge : 

Per  cent.  Per  cent. 

Ammonia 2.22  ..        0.884 

Phosphate  of  lime. .     2 . 05  . .  13.57 

Organic  matter 43 . 72  . .  31 . 74 

The  former  he  regards  as  of  the  esti- 
mated value  of  £1  16s.  5^d.,  and  the 
latter  of  £1  15s.  per  ton. 

COMPOUNDS      OF      IKON      AND      ALUMINA 
(SULPHATED    CLAY). 

Birds  Process.     Six  cwt.  of  powdered 


136 

clay  is  treated  with  120  Ibs.  of  sulphuric 
acid,  and  the  mixture  allowed  to  stand 
for  a  week. 

The  following  are  places  where  the 
process  has  been  used : 

Stroud (Gloucester shire).  This  solution 
of  sulphate  of  alumina  and  iron  is  used 
in  quantity  equal  to  28  to  37  grs.  of 
mixed  sulphates  per  gallon,  at  Stroud 
(population  8,000)  in  Gloucestershire,  to 
defecate  200,000  gallons  of  sewage. 
The  treated  sewage  is  allowed  to  run 
into  settling  tanks  passing  from  one  to 
another  through  straw  niters,  and  finally 
filtered  through  coke  filters.  The  sludge 
is  dried,  and  made  into  a  manure  by  ad- 
mixture with  sulphate  of  ammonia  and 
phosphate  of  lime. 

The  Stroud  sewage  was  examined  and 
reported  on  by  the  Kivers  Pollution 
Commissioners  in  1868,  when  a  solution 
containing  6  cwt-  of  pulverized  clay  acted 
on  by  120  Ibs.  of  sulphuric  acid  was 
added  to  200,000  gallons  of  sewage. 
They  record  the  effluent  as  inodorous, 


137 

but  not  of  a  high  degree  of  purity.  (See 
1st  Keport,  1868,  p.  58.) 

Cheltenham.  Bird's  process  was  adopt- 
ed at  Cheltenham  in  1868.  It  was  said 
not  to  be  a  success. 

Northampton.  In  1872,  Northampton 
sewage,  which  was  then  1,000,000  gallons 
a  day,  was  defecated  with  crude  sulphate 
of  alumina  and  iron,  made  by  the  action 
of  sulphuric  acid  on  a  ferruginous  clay. 
Three  cwt.  of  chamber  sulphuric  acid 
were  added  to  2  tons  of  clay  in  a  wooden 
trough,  and  allowed  to  remain  in  contact 
for  a  week.  The  solution  was  generally 
found  to  contain  about  15  cwt.  of  a  sul- 
phated  ferruginous  compound.  There 
were  six  of  these  troughs  in  use — the 
entire  soluble  contents  of  one  trough 
being  used  daily.  The  flocculation  was 
imperfect  from  the  want  of  an  efficient 
stirring  apparatus.  Moreover,  the  acid 
of  the  chemicals  caused  effervescence  with 
the  carbonates  present,  a  scum  being 
formed  from  the  rise  of  the  suspended 
matters.  This,  however,  was  kept  back 
in  the  firdt  tank  by  cross-bars.  The  sew- 


138 

age  then  flowed  into  a  second  tank,  and 
finally  over  a  weir  into  a  channel  a  mile 
in  length,  when  it  was  discharged  into 
the  river.  The  river  itself  was  clean,  the 
aquatic  vegetation  healthy,  and  fish 
abundant. 

The  samples  given  below  are  averages 
of  many  samples  taken  over  24  hours. 
The  effluents  generally  were  clear  and 
inoffensive. 

/ Matters  in  Solution. ^ 

Oxygen  required 
Total  solids,    to  oxidize.  Ammonia. 

Raw  sewage 73.60     ..     2.265     ..  4.98 

Effluent,  1st  tank.  70.16     ..     1.980     ..  4.19 
Effluent,  2d  tank.  70.65     ..     1.243     ..3.247 

* Matters  in  Suspension. > 

Total  solids.      Organic.       Mineral. 

RawseWage 13.83     ..     8.48     ..     5.37 

Effluent,  1st  tank.     4.97     ..     2.91     ..     2.06 
Effluent,  2d  tank.     1.74     ..     1.11     ..     0.63 

About  400  tons  of  sludge  were  removed 
per  week.  This  was  mixed  with  sifted 
ashes  (48  tons)  and  burnt  refuse  (20  tons), 
and  found  a  market  at  3s.  per  ton. 

In  1875,  the  proprietors  of  Bird's  pro- 
cess brought  an  action  against  the  pro- 
prietors of  the  Coventry  process  for 


139 

infringement,  in  which  they  were  unsuc- 
cessful. 


A  process  ( Cobleys  patent)  similar  to 
the  one  just  described  (the  precipitants 
being  said  to  consist  of  iron,  alumina  and 
carbon)  is  in  use  at  Crewkerne,  the  precipi- 
tant being  placed  in  a  box  with  perforated 
sides,  the  sewage  being  allowed  to  How 
through  the  box  by  which  contact  with 
the  precipitant  was  secured.  There  is  no 
stirrer,  but  sufficient  mixing  is  said  to  be 
effected  by  the  means  described.  The 
patentee  states  that  the  precipitant  can 
be  supplied  (exclusive  of  a  small  royalty) 
at  £2  per  ton.  A  good  effluent,  which 
does  not  undergo  putrefactive  change  by 
keeping,  is  stated  to  be  produced. 

At  Hertford  (population  9,000)  the 
sewage  is  treated  with  a  solution  of  sul- 
phate of  iron  (1  part),  lime  (2  parts),  and 
sulphate  of  alumina  (2£  parts).  It  flows 
into  subsidence  tanks  (7  in  all,  5  being 
used  continuously  ),  and  finally  through 
a  coke  filter. 


140     , 

LIME  AND  SALTS  or    ALUMINA  (COVENTRY 
PROCESS). 

Anderson,  of  Coventry,  suggested  the 
use  of  lime  and  an  aluminous  compound, 
prepared  by  adding  1  part  of  common 
sulphuric  acid,  mixed  with  its  own^'bulk 
of  water,  to  2  parts  of  clay  (shale  having 
also  been  used).  The  mixture  is  to  be 
set  aside  in  a  warm  place  until  it  appears 
white  on  the  surface. 

One  pound  of  this  mixture  is  to  be  well 
agitated  with  100  gallons  of  sewage,  and 
a  J  Ib.  of  lime  (as  cream  of  lime)  after- 
wards added.  He  advises  that  the  defe- 
cated sewage  be  allowed  absolute  rest 
for  twenty-four  hours,  the  clear  effluent 
being  then  drawn  off,  and  the  sludge 
removed. 

Odling  gives  the  following  results  by 
this  process : 

f Matters  in  Solution. , 

Total  solids.  Organic  matter.  Ammonia. 
Raw  sewage..  42.77     ..       8.33     ..       0.77 
Effluent 56.28     ..       6.30     ..       0.84 

Matters  in  Suspension. , 

Total  solids.         Organic.          Mineral. 
Raw  sewage..  89.74     ..     51.66     ..     38.08 
Effluent 1.61     ..       0.91     ..       0.70 


141 

Both  Odling  and  Voelcker  reported 
highly  of  this  effluent,  as  thoroughly 
deprived  of  noxious  qualities. 

The  sludge  is  valued  by  Voelcker  at 
30s.  a  ton.  He  gives  the  following  anal- 
yses : 

Moisture 12.01  ..  15. tO 

Organic  matter 26 . 89  . .  31 . 86 

Phosphate  of  lime. .     2.60  . .  2.55 

Mineral  salt 6.61  ..  10.33 

Silica,  etc 51.89  ..  39.56 

100.00     ..  100.00 
Ammonia =     1.39     ..       1.22 

At  Coventry  the  use  of  this  process 
was  commenced  in  1874.  It  has  been 
ably  supervised  for  many  years  by  Mr. 
Melliss,  C.  E.  There  are,  at  the  present 
time,  four  precipitating  tanks  worked  on 
the  continuous  principle.  The  effluent 
flows  through  filter  beds  occupying  9 
acres,  used  intermittently,  and  is  ulti- 
mately discharged  into  the  River  Sher- 
bourne. 

The  sewage  of  Coventry  is  about 
2,000,000  gallons  daily,  very  foul,  and 
much  colored  with  dye  refuse,  etc.  It 


142 

needs  far  more  chemicals  than  average 
sewage.  The  sludge  produced  is  about 
25  tons  per  day  (90  per  cent,  moisture). 
About  2  tons  of  crude  sulphate  of 
alumina  (but  of  which  2-5ths,  being  in- 
soluble in  water,  is  not  put  into  the  sew- 
age), and  10  cwt.  of  lime  are  used  daily. 
The  cost  for  chemicals  is  said  to  be  £1 
14s.  per  1,000,000  gallons,  and  the 
entire  cost  (including  rent,  capital  on 
works,  management,  etc.)  about  £4  14s. 
per  1,0.00,000  (=  1.8-J-  per  head). 

Formerly,  one  portion  of  the  sludge 
was  got  rid  of  in  a  semi-dry  condition  at 
7s.  per  ton,  whilst  another  portion,  dried 
and  reduced  to  a  portable  condition, 
fetched  £2  per  ton.  Some  of  the  sludge 
was  also  "  fortified  ''  by  added  chemicals, 
and  fetched  from  £5  to  £6  per  ton. 

A  similar  process  was  also  in  use  at 
Nuneaton  from  1872  to  1876,  when  the 
arrangements  between  the  Local  Board 
and  the  General  Sewage  and  Manure 
Company  fell  through,  from  some  mis- 
understanding respecting  the  average 
daily  flow.  Nuneaton  sewage  is  offensive, 


143 

owing  to  the  presence  of  manufacturing 
refuse.  From  400,000  to  500,000  gallons 
were  treated  daily.  The  effluent  was 
filtered  through  2  acres  of  land.  The 
yield  of  manure  was  about  1  ton  daily. 
The  cost  was  as  nearly  as  possible  the 
same  as  at  Coventry. 

THE  ABC  PROCESS  — THE  NATIVE  GUANO 
COMPANY. 

The  patent  of  the  Messrs.  Sillars 
and  Wigner  (1868)  claim  the  use  of  alum, 
blood,  and  clay  (hence  termed  the  ABC 
process),  with  other  agents,  viz.,  com- 
pounds of  manganese  and  magnesium, 
chloride  of  sodium,  animal  and  vegetable 
charcoal,  with  the  object 

(1.)  Of  deodorizing  and  purifying  sew- 
age by  means  of  these  chemical  sub- 
tances,  and  so  obtaining  a  sediment 
which  may  be  used  as  manure. 

(2.)  The  deodorizing  and  purifying 
sewage  by  means  of  the  mud  already 
precipitated  from  sewage  as  above  de- 
scribed. 


144 

(3.)  The  addition  of  an  acid  to  the  mud 
in  order  to  retain  ammonia,  and  so  fit  it 
for  use  as  a  manure. 

The  precise  composition  of  the  pre- 
cipitating material  has  been  changed 
from  time  to  time.  When  first  used  at 
Leicester,  in  1868,  the  precipitating  mix. 
ture  consisted  of  : 

Parts. 

Alum 600 

Blood 1 

Clay ,...1,900 

Magnesia 5 

Manganate  of  potash 10 

Burnt  clay 25 

Chloride  of  sodium 10 

Animal  charcoal 15 

Vegetable  charcoal 20 

Magnesian  limestone 2 

These  were  mixed  with  water,  and 
added  to  the  sewage,  until  no  further 
precipitate  resulted.  About  4  Ibs.  of  the 
mixture  were  required  to  every  1,000 
gallons  of  sewage  (=  28  grs.  per  gallon). 
The  treated  sewage  then  flowed  into  sub- 
sidence tanks,  where  the  sediment  was 
allowed  to  deposit.  This  sediment  was 


145 

used  five  or  six  times  over  as  a  precipi- 
tant, until  its  power  in  this  respect  was 
exhausted.  After  the  sludge  had  been 
dried,  a  small  quantity  of  acid  (preferably 
sulphuric  acid)  was  added  to  fix  the  am- 
monia, in  which  state  it  was  claimed  to 
be  a  valuable  manure. 

In  1869,  the  process  was  worked  at 
Leamington,  the  composition  of  the  pre- 
cipitating mixture  being: 

Parts. 

Alum 259 

Clay 896 

Charcoal 56 

Clay  blood 40 

Carbonates  of  soda  and  potash . .         6 

Previous  precipitate         14 

Perchloride  of  iron  solution 1  pint. 

This  mixture  was  added  in  the  pro- 
portion of  about  51  grs.  per  gallon,  at  a 
cost  of  £15  18s.  per  million  gallons  of 
sewage. 

The   mixture   used  at  Leamington  in 

1870  was  as  follows  : 

Parts. 

Ammonia  alum 336 

Clay 672 

Animal  charcoal 15 

Vegetable  charcoal 20 

Sulphate  of  magnesium 20 

Clay  blood 4 


146 

Of  this  composition  56  grains  per 
gallon  was  found  to  be  necessary. 

1873,  the  process  was  used  for  a  short 
time  at  Crossness  for  the  treatment  of 
500,000  gallons  daily  of  the  sewage  at  the 
Southern  Metropolitan  Outfall.  The 
mixture  used  had  the  following  com- 
position : 

Parts. 

Sulphate  of  alumina 5 

Charcoal 29 

Clay 26 

Mixed  with  a  little  blood. 

This  was  added  in  the  proportion  of 
224  grains  per  gallon,  and  yielded  12.33 
tons  of  manure  per  million  gallons  of 
sewage  (5.25  tons  from  sewage,  and  7.08 
tons  from  the  added  chemicals),  the  in- 
gredients costing  £24  9s.  8d. 

Tottenham,  Hastings,  Bolton  (1872), 
Southampton,  and  Leeds  afterwards 
adopted  the  process,  but  in  all  it  was 
abandoned  on  the  ground  of  cost.  At 
Southampton  a  contract  to  deal  with  the 
sewage  was  canceled  after  £10,000  had 
been  spent  on  works,  owing  to  some 


147 

erroneous  expectations  respecting  profits. 
At    Bolton,    1872-1873,    the   chemicals 
used  were  as  follows : 

Parts. 

Sulphate  of  alumina 71 

Clay 132 

Carbon  (waste  from  prussiate  of 

potash  factory) 81 

Blood,  small  quantity. 

This  mixture  was  added  at  the  rate  of 
about  90  grains  per  gallon.  The  quantity 
of  sewage  treated  was  2,500,000  gallons 
daily.  The  process  was  abandoned  on 
the  ground  of  expense. 

At  Leeds  in  1870  (sewage  9,000,000 
gallons  daily,  of  which  the  ABC  Company 
were  to  deal  with  2,000,000)  the  pre- 
cipitating mixture  employed  was : 

Parts. 

Alum 5,964 

Carbon  (refuse  from  prussiate  of 

potash  factory) 4,480 

Clay 7,460 

Blood  mixture 56 

Lime .. .      186 

About  120  grains  per  gallon  of  this 
mixture  was  employed.  The  cost  for 


148 

chemicals  per  million  gallons  was  £7  5s. 
The  Company  abandoned  the  works  on 
June  1st,  1873.  In  June,  1875,  however, 
they  again  treated  the  Leeds  sewage  for 
one  week  with  the  following  precipitating 
mixture  : 

Parts. 

Lime 15,990 

Animal  carbon 13,556 

Alum 8,076 

Clay 16,848 

Carbolic  acid 28 

About  forty  grains  of  this  mixture  was 
used  per  gallon  of  sewage,  at  a  cost  of 
£2  8s.  lOd.  per  1,000,000  gallons. 

Another  trial  was  made  for  one  week 
in  January,  1876,  when  the  cost  of  chemi- 
cals was  found  to  be  £3  5s.  9d.  per 
million  gallons. 

The  process,  as  carried  out  at  Leam- 
ington (population  20,000,  sewage  600,- 
000  gallons  daily  in  dry  weather),  was 
successful.  The  ABC  mixture  was 
stirred  into  the  sewage  in  a  circular  tank, 
from  which  it  passed  into  two  settling 
tanks,  each  set  being  used  for  one  week, 


149 

there  being  three  sets  of  tanks  for  alter- 
nate working.  The  effluent  then  flowed 
into  a  channel  850  feet  in  length,  10  feet 
wide,  4  feet  deep,  the  last  third  of  which 
was  converted  into  a  filter  of  sand  and 
animal  charcoal,  having  a  superficial  area 
of  3,000  square  feet.  The  sludge  was 
converted  into  paste  by  centrifugal  ma- 
chines, revolving  1,500  times  per  minute, 
and  afterwards  further  dried  by  exposure 
to  air.  It  was  then  sprinkled  with  dilute 
sulphuric  acid  (1  of  acid  to  6  water),  the 
acid  being  used  in  the  proportion  of  one 
per  cent,  of  the  manure.  It  was  after- 
wards heaped  for  a  fortnight,  during 
which  time  it  heated  considerably,  form- 
ing a  rotten  compost,  which  was  further 
dried  and  sold  for  manure. 

About  28  grains  per  gallon  of  the  A  B 
C  mixture  was  employed,  whilst  the  dried 
precipitate,  containing  20  per  cent,  of 
moisture,  weighed  about  80  grains. 
Analyses  of  the  effluent  at  Leamington, 
as  reported  on  by  Dr.  Letheby,  are  as 
follows  : 


150 


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151 

It  will  be  noted  in  these  analyses  that 
the  chloride  of  sodium  in  the  effluent  is 
less  than  that  of  the  original  sewage. 
This  may  be  partly  explained  by  its  di- 
lution with  subsoil  water,  and  also  by 
the  fact  shown  by  Voelcker  and  Way 
that  marly  soils  possess  the  power  of  re- 
moving alkaline  chlorides  from  their 
solutions. 

At  Hastings  the  works  were  situate  on 
the  seashore.  The  ABC  material  was 
agitated  by  a  machine  mixer  with  the 
sewage,  and  after  flowing  through  sub- 
siding tanks,  was  discharged  into  the 
sea. 

The  ABC  process  depends  in  great 
measure  on  the  alumina  as  a  precipitating 
agent.  It  is  doubtful  whether  the  blood 
is  of  any  service,  as  it  can  scarcely  be 
urged  that  in  the  quantity  in  which  it  is 
added,  the  fibrin  can  be  of  much  value 
as  an  agent  for  entangling  suspended 
matter.  The  clay  is  mainly  a  weighting 
agent,  to  assist  the  rapid  (subsidence  of 
the  suspended  impurities. 

Of   course  the  quality  of  the  manure 


152 

must  depend  on  the  quality  of  the  sewage. 
Hence,  as  we  should  expect,  its  composi- 
tion is  not  absolutely  constant.  Against 
the  valuations  of  authorities  we  have  the 
indisputable  fact  that  it  is  being  sold 
continuously  for  about  £3  10s.  per  ton. 

PHOSPHORIC    ACID,    MAGNESIA    AND    LIME. 

HerapatWs  Process— .Bly the1  s  Process. — 
The  object  of  this  mixture  as  a  sewage 
precipitant  is  to  fix  the  ammonia  (as  an 
insoluble  ammonio-phosphate  of  magne- 
sia) which  in  the  employment  of  lime,  or 
iron  and  alumina  salts,  remains  in  solu- 
tion in  the  effluent,  and  consequently  is 
lost.  The  lime,  however  (in  common 
•with  iron  and  alumina  salts)  precipitates 
the  phosphoric  acid  in  the  sewage.  The 
use  of  sulphate  or  chloride  of  magnesium 
as  a  precipitant,  in  order  to  form  the  in- 
soluble ammonio-phosphate  of  magnesia, 
was  first  suggested  by  Sir  James  Murray. 
Herapath,  in  1853,  patented  a  process 
for  the  use  of  magnesia  or  one  of  its 
compounds,  in  order  to  precipitate  the 


153 

ammonia  and  phosphoric  acid  "  at  or 
about  the  same  time  as  the  deodorization 
of  the  same  sewage  is  effected  by  the 
addition  of  some  chemical  agent  which 
will  not  decompose  ammonia  or  its  salts." 

With  this  object  he  employed  a  mix- 
ture of  1  part  of  sulphate  of  iron,  and  4 
parts  of  burnt  magnesian  limestone. 
The  process  was  tried  at  the  sewage 
Works  of  St.  Thomas,  near  Exeter,  but* 
proving  unremunerative,  was  abandoned. 

Murray  and  Her apat fa's  process  did 
nofc  meet  with  the  approval  of  Hofmann 
and  Witt,  on  the  ground  that  1  part  of 
the  ammonio-phosphate  of  magnesia  is 
soluble  in  45,000  parts  of  water  contain- 
ing free  ammonia  and  in  15,000  parts  of 
pure  water,  whilst  in  a  water  containing 
a  salt  of  ammonia,  it  was  soluble  to  the 
extent  of  1  in  7,000  parts. 

In  1858,  Blythe  (Consulting  Chemist 
of  the  Board  of  Health)  patented  the  use 
of  a  solution  of  phosphate  of  magnesia 
in  combination  with  lime  or  other  pre- 
cipitating agent. 

The  following  is  his  description  of  the 
process : 


154 

"  Superphosphate  of  magnesia  is  first 
to  be  prepared  by  the  mutual  decomposi- 
tion of  superphosphate  of  lime  and  a  salt 
of  magnesia,  the  superphosphate  of  lime 
being  obtained  from  bones,  bone-ash, 
apatite,  phosphorite,  coprolite,  phosphate 
of  alumina,  phosphate  of  iron,  phosphate 
of  copper,  or  any  other  substance  con- 
taining phosphoric  acid,  by  the  aid  of 
sulphuric  or  muriatic  acid,  or  other  apid, 
the  proportions  being,  in  the  case  of 
phosphate  of  lime,  one  ton  of  phosphate 
to  half  a  ton  of  sulphuric  acid  of  com- 
merce, previously  mixed  with  three  times 
its  weight  of  water,  or  three  quarters  of 
a  ton  of  hydrochloric  acid  of  commerce 
diluted  with  twice  its  weight  of  water. 
These  are  allowed  to  stand  together  for 
two  or  three  days,  being  frequently 
stirred,  and  then  they  are  mixed  with  a 
ton  of  sulphate  of  magnesia,  dissolved  in 
a  small  quantity  of  water,  say  a  little 
more  than  its  own  weight.  Powdered 
charcoal  is  then  added  in  sufficient  quan- 
tity (about  one  ton)  to  bring  the  mixture 
into  a  solid  and  convenient  form  for 


155 

transport.  When  used  for  the  purifica- 
tion of  sewage,  it  is  to  be  dissolved  in 
water,  and  added  to  the  sewage  in  the 
proportion  of  five  parts  of  the  phosphate 
to  every  100  parts  of  solid  matter  in  a 
gallon  of  the  sewage.  The  whole  is  then 
to  be  well  mixed  and  thoroughly  incor- 
porated by  means  of  an  agitator.  If  the 
sewage  does  nob  contain  enough  free 
ammonia  or  other  alkali  to  neutralize  and 
precipitate  all  the  superphosphate  of 
magnesia,  lime  is  to  be  added,  in  the  form 
of  milk  of  lime,  until  the  sewage  is  faintly 
alkaline  to  test  paper.  By  this  means 
the  ammonia-phosphate  of  magnesia  is 
thrown  down  as  a  flocculent  precipitate, 
which  carries  with  it,  after  the  manner  of 
a  clarifier,  any  insoluble  impurities  sus- 
pended in  the  liquid.  In  like  manner, 
instead  of  lime,  he  claims  the  use  of  any 
other  alkali  or  alkaline  earth,  as  potash, 
soda,  magnesia  or  magnesian  limestone, 
or  alumina.  He  thus  produces  a  valu- 
able manure,  containing,  as  he  supposed, 
the  ammonia,  as  well  as  the  nitrogenous 
organic  matter  of  the  sewage,  and  the 


156 

phosphoric  acid  employed ;  i  while  the 
supernatant  liquor  being  freed  from  am- 
monia and  nitrogenous  matter,  liable  to 
undergo  putrefaction,  becomes  deodor- 
ized, and  may  be  either  applied  to  the 
irrigation  of  land,  or  run  off  into  the 
ordinary  channels  of  drainage  without 
fear  of  creating  any  nuisance  or  offense.'  " 

Way,  in  1861,  in  the  second  report  of 
the  Commission  to  inquire  into  the  best 
mode  of  distributing  the  sewage  of  towns, 
condemned  the  process  as  the  most  costly 
of  all  the  plans  that  have  been  proposed, 
but  on  grounds  that  scarcely  commend 
themselves  to  our  judgment.  lam  ready 
to  admit  that  the  process  may  fail  in  re- 
moving the  ammonia  to  the  extent  indi- 
cated by  the  patentee,  but  how  it  can 
possibly  fail  in  removing  the  phosphoric 
acid  (I  am  arguing  now  on  chemical 
grounds),  as  Way's  analyses  show  is  be- 
yond comprehension.  The  only  explana- 
tion can  be  that  Mr.  Way  did  not  use 
sufficient  lime. 

Many  experiments  were  made  with 
Blythe's  mixture,  of  which  the  following 


157 

are  illustrations.  Superphosphate  of  mag- 
nesia was  added,  in  the  proportion  of  10.3 
grains  of  phosphoric  acid  per  gallon,  and 
:hen  an  excess  of  lime  until  the  sewage 
was  faintly  alkaline. 

, —       — Matter  in  Solution. » 

Total     Phosphoric     Am-      Oxygen 
solids.          acid.       monia.  required. 
Metropolitan. 

Raw  sewage.  68.33  ..  .64  ..  6.33  ..  2.54 

Effluent 90.02  ..  .60  ..  6.24  ..  1.41 

Coventry. 

Raw  sewage.  46.61   ..  .53  ..  1.16  ..  .78 

Effluent 68  07  . .  .05  . .   1 .06  . .  .43 

Matters  in  Suspension. » 

Total  solids.       Organic.          Mineral. 
Metropolitan. 


Raw  sewage  .  . 
Effluent    

47.42  . 
0 

.  27.51  . 
0 

.  19.91 
0 

Coventry. 
Raw  sewage  .  . 
Effluent  .  . 

21.11  . 
0 

.  8.87  . 
0 

.  12.24 
0 

The  dried  precipitates  had  the  following 
percentage  composition : 

Organic  matter 28.06  . .  12.16 

Phosphate  of  lime 27.11  . .  32.65 

Earthy  matters 35.30  . .  45. 60 

Sand,  etc 9.53  . .        9.59 


100.00  100.00 

Nitrogen  equal  to  ammonia.. 1.61  0.99 


158 

The  process  purified  the  sewage  suc- 
cessfully. One  ton  3  cwt.  of  the  super- 
phosphate compound  and  4  cwt.  of  lime 
was  found  on  an  average  to  be  required 
for  1,000,000  gallons.  This  produces  3 
tons  1  cwt.  of  a  manure  valued  at  £3  14s. 
per  ton,  the  chemicals  and  labor  to  pro- 
duce which  cost  £1  15s.,  leaving  a  net 
profit  of  £1  19s. 

Blythe's  later  experiments  showed 
that  the  magnesian  compound  might  be 
omitted,  and  that  the  precipitated  phos- 
phate of  lime  was  as  valuable  for  plants 
as  the  original  superphosphate. 

Arrangements  had  been  made  to  try 
the  process  at  Southampton  and  Leicester, 
but  fell  through,  owing  to  the  death  of 
the  patentee. 

PHOSPHORIC  ACID,  LIME,  AND  ALUMINA. — 

PHOSPHATE  SEWAGE  PROCESS. 
The  patent  of  Mr.  David  Forbes,  F.  E. 
S.,  and  of  Dr.  Astley  Paston  Price  was 
taken  out  in  1870.  It  consisted  in  the 
use  of  an  acid  solution  (sulphuric  acid 
being  generally,  employed)  of  natural 
phosphate  of  alumina,  with  or  without 


159 

lime  or  carbonate  of  lime.  The  object 
was  to  employ  a  precipitant  of  manurial 
value,  in  order  to  obtain  a  compost  of 
high  fertilizing  power. 

The  phosphate  of  alumina  was  obtained 
from  the  West  Indies,  where  it  occurs  in 
such  enormous  quantities  that  on  one 
island  alone  the  deposit  is  estimated  at 
9,000,000  tons.  It  contains  about  38 
per  cent,  of  phosphoric  acid  and  25  per 
cent,  of  alumina,  with  about  2.5  per  cent, 
of  peroxide  of  iron.  It  was  formerly 
supposed  to  be  phosphate  of  lime,  but 
analysis  shows  that  the  material  does 
not  contain  more  than  2  per  cent,  of  lime. 

Experiments  with  London  and  Coven- 
try sewage,  in  which  was  added  33  grains 
per  gallon  of  the  phosphatic  material  (= 
10.38  grains  of  phosphoric  acid)  dissolved 
in  its  own  weight  of  commercial  sulphuric 
acid,  gave  results  as  follows : 


-Matters  in  Solution. — 


Total     Phosphoric    Am-  Oxygen 

solids.  acid.       monia.  required. 
London. 

Raw  sewage.  68.33  ..  0.64  ..  6.33  ..  2.54 

Effluent 100.07  ..  0.68  ..  5.70  ..   1.44 

Coventry. 

Raw  sewage.  46.61  ..  0.53  ..  1.16  ..  0.78 

Effluent..      .  82.59  ..  0.60  ..  1.04  ..  0.47 


160 

/ Matters  in  Suspension. > 

Phosphoric 
Total  solids.    Organic.      Mineral,    acid. 

London". 

Kaw  sewage. 47. 42  ..  27.51  ..  19.33  ..  0.68 

Effluent 0       ..       0  ,' .       0       ..0 

Coventry. 

Raw  sewage. 21. 11   ..     8.87  ..  11.96  ..  0.28 

Effluent 0       ..       0  ..       0       ..0 

The  dried  precipitate  gave  as  follows: 

London  Covent'y 
sewage,  sewage. 

Organic  matter 24.80  .  10.40 

Phosphate  of  lime 16.82  .  22.11 

Carbonate  of  lime  and  magnesia  49.39  .  58.14 

Silica,  etc 8  99  .  9.34 


100.00    100.00 
Nitrogen  equal  to  ammonia. ...      1.41   .     0.91 

The  effluent  was  clear  and  without 
smell,  much  soluble  organic  matter  being 
removed.  The  process,  however,  is  pe- 
culiar in  this  respect,  that  if  no  lime  be 
added  after  the  precipitating  material, 
much  soluble  phosphate  will  remain  in 
solution.  The  effluent  may  then  be  used 
for  irrigation,  no  nuisance  being  likely  to 
result  from  the  use  of  the  clarified  water, 
the  manurial  value  of  which  will  be  con- 


161 

siderable.  In  other  words,  we  strengthen 
(the  patentees  would  say)  the  manurial 
value  of  the  sewage,  and  purify  it  by  the 
same  operation. 

If  lime  be  used,  the  deposit  may  be 
made  to  contain  any  proportion  of  phos- 
phate of  lime  (indeed  it  may  be  rendered 
almost  pure  bone  earth),  necessary  to 
pay  its  cost  of  carriage  to  a  distance. 

Thus  to  effect  a  good  sanitary  result  a 
small  quantity  only  of  precipitating  mat- 
ter is  required,  whilst  a  commercial  suc- 
cess may  be  effected  by  the  use  of  a  large 
quantity  of  the  precipitant.  Thus,  if  two 
tons  of  the  phosphate  be  added  to  every 
1,000,000  gallons  of  London  sewage,  it 
would  yield  four  or  five  tons  of  manure, 
containing  15  to  18  per  cent,  of  phos- 
phoric acid,  whilst  if  three  tons  be  added 
per  million,  a  manure  would  be  obtained 
worth,  according  to  Voelcker,  £7  7s.  per 
ton,  and  having  a  composition  as  follows : 

Per  cent. 

Moisture 3.98 

Organic  matters . .  20 . 11 

Phosphoric  acid..  28.52=62.26  tribasic  phos- 
phoric of  lime. 


162 

Per  cent. 

Lime 13.09 

Alumina,  etc 29.95 

Sand,  etc 4.35 


100.00 
Nitrogen  0.57=to  ammonia  0.69. 

The  only  place  where  the  process  was 
worked  to  which  we  need  refer  is  Hertford, 
where  the  process  was  in  operation  for 
two  years  (1876-1877).  The  results  were 
good,  but  no  details  are  given  as  to  cost. 
The  company  paid  £100  per  year  rent 
for  the  works,  and  received  £300  per 
year  as  a  subsidy  from  the  corporation, 
i.e.,  at  the  rate  of  7d.  per  head  of  the 
population. 

W/ntthreacTs  Process  (1872).  — The 
patentee  employs  superphosphate  with  a 
little  milk  of  lime,  the  object  being  to  re- 
cover the  phosphoric  acid  in  the  sludge. 

Dugald  Campbell's  Process.  (1872). — ' 
The  patentee  employs  superphosphate 
and  some  lime.  It  was  tried  at  Totten- 
ham in  1872  for  six  days  on  3,500,000 
gallons,  at  a  cost  for  chemicals  of  £16  6s. 
5d.  per  million  gallons,  yielding  6.3  tons 


163 

of  manure  per  million,  valued  at  £5  per 
ton. 

It  was  also  tried  experimentally  (1873 
to  1875)  on  the  metropolitan  sewage, 
when  the  chemicals  required  to  produce 
a  good  effluent  were  found  to  cost  at  the 
rate  of  £ 22  6s.  per  million  gallons.  The 
dry  manure  was  valued  at  from  £3  15s.  to 
£4  15s.  per  ton. 

SALTS  OF  IRON. 

Brown  (Feb.  1847)  patented  the  use  of 
the  sulphates  and  chlorides  of  iron  as 
sewage  disinfectants,  and  JEJllerman(Oci. 
1847)  the  use  of  the  chlorides  and  pyroly- 
nates  (acetates)  of  iron.  Ellerman's  fluid 
(price  Is.  6d.  a  quart  retail,  9d.  wholesale), 
contained  from  24  to  43  per  cent,  of  the  iron 
salts  named,  and  had  a  specific  gravity  of 
from  1336  to  1443. 

Dales  fluid  (sp.  gr.  1450,  price  6d.  per 
gallon)  was  a  strong  solution  of  per- 
chloride  of  iron,  and  was  proposed  by 
Hofmann,  Frankland,  and  Miller,  for  de- 
odorizing the  Thames  during  the  hot 
summers  of  1857  and  1860,  on  the  ground 


164 

that  it  compared  favorably,  as  regards 
cost,  with  lime  or  chloride  of  lime.  Thus 
they  said  1,000,000  gallons  of  London 
sewage  required  for  deodorization  the 
following  quantities  of  the  several  ingre- 
dients named : 

Cost. 
£   s.     d. 
86    gallons  of  Dale's  fluid....  113    0 

400    Ibs.  of  chloride  of  lime..  2    2  10 £ 
132£  bushels  of  lime 3    6    6 

They  remark  that  the  sewage  treated 
with  lime  became  offensive  after  three 
days — with  chloride  of  lime  after  four 
days-whilst  that  treated  with  perchloride 
of  iron  did  not  become  offensive  even 
after  nine  days.  The  use,  however,  of  the 
iron  was  objected  to  by  Odling  and  Lethe- 
by,  both  urging  that  a  black  mud  would 
form  in  the  river,  which,  after  a  time, 
would  undergo  putrefactive  changes,  and 
be  more  unsightly  than  even  the  sewage. 
Letheby  also  urged  the  quantity  of  arsenic 
in  tJae  perchloride  as  an  unanswerable  ob- 
jection to  its  employment  as  a  precipitant 
where  the  sludge  is  not  removed  before 
the  treated  sewage  is  allowed  to  escape 
into  the  river. 


165 

Dale's  liquid  (130  gallons  to  1,000,000) 
was  used  at  Croydon  in  1852  and  1860. 
The  results  were  not  satisfactory,  because 
the  suspended  matter  was  imperfectly  re- 
moved, the  iron  sulphide  giving  the  ef- 
fluent a  black  and  polluted  appearance. 

Dover 's  patent  (1851)  claims  the  use  of 
acids  with  iron  filings  or  oxide  of  iron 
and  protosulphate  of  iron,  the  defecated 
sewage  being  afterwards  filtered  through 
charcoal,  peat,  etc. 

Mudies  disinfectant,  a  preparation  of 
dry  copperas,  is  valuable  for  the  deodori- 
zation  of  drains,  etc.,  owing  to  its  prop- 
erty of  absorbing  ammonia  and  sulphur- 
etted hydrogen.  It  is  hardly  suited  for 
the  defecation  of  sewage,  although  it  acts 
well  as  a  general  disinfectant,  for  which 
purpose  it  is  largely  used  in  the  French 
slaughter-houses. 

LIME,  SULPHATE  or  IRON,  AND  COAL 
DUST. — HOLDEN'S  PROCESS. 

This  mixture,  as  a  sewage  precipitant, 
was  patented  by  Jules  Houzeau  and 
Devedeix  (1866),  and  was  used  at  Brad- 


166 

ford  by  Mr.  Holden  (hence  known  as 
Holdens  Process).  The  sulphate  of  iron 
was  to  be  added  first,  and  afterwards 
milk  of  lime  mixed  with  coal  dust.  The 
use  of  clay  is  also  mentioned  in  Holden's 
patent.  The  treated  sewage  then  flows 
into  subsiding  tanks.  A  clear  and  inodor- 
ous effluent  can  be  obtained,  about  one- 
half  of  the  dissolved  organic  matter 
being  precipitated.  The  manure  is  of 
little  value. 

Bradford. — The  process  was  tried  in 
1868  on  130,000  gallons  daily.  It  was 
reported  against  by  the  Kivers  Pollution 
Commissioners,  as  giving  a  clear  effluent, 
but  of  a  quality  worse  than  the  original 
sewage,  founding  their  opinion  on  the 
quantity  of  organic  nitrogen  present. 
They  supposed  that  the  putrescible  or- 
ganic matters  in  suspension  passed  into 
solution  by  this  treatment.  Further,  they 
considered  the  hardness  of  the  effluent 
an  objection  to  its  being  allowed  to  pass 
into  water-courses. 

Marsden  and  Collins  Process  consists 
in  the  use  of  lime,  carbon  waste  from  the 


167 

prussiate  manufacture,  house  ashes,  soda, 
and  perchloride  of  iron. 

This  process  was  used  in  1874  at 
Boltoti,  in  dealing  with  one  sixth  of  the 
sewage  (population,  93,000).  The  cost 
of  chemicals  was  given  at  £1  7s.  3d.  per 
million  gallons  of  sewage,  the  total  cost 
being  £7  14s.  5£d.  per  million. 

Hansons  Process  (1875)  employs  lime, 
black  ash  (tank  waste,  or  refuse  from 
alkali  works,  containing  sulphides  of  cal- 
cium and  sodium),  and  red  haematite 
treated  with  sulphuric  acid. 

This  process  was  tried  at  Leeds,  the 
chemicals  used  being  in  the  proportion 

of: 

Tons.  Cwts. 

Lime 20      0 

Black  ash 4      0 

Red  haematite  and  oil  of  vitriol. .     1      6 

Two  tons  16  cwt.  and  1  qr.  were  added 
to  every  1,000,000  gallons,  at  a  cost  of 
£2  5s.  8d.  per  million.  The  effluent  was 
said  to  be  good.  Its  use  was  discon- 
tinued in  April,  1876. 

A  modification  of  this  process  is  now 


168 

in  use  at  Leyton.  The  process  was  adopt- 
ed in  1882  by  the  Golcar  Local  Board. 
G-oodaWs  Process  (1875)  employs  lime, 
animal  charcoal,  ashes,  and  iron  liquor 
(solution  of  sulphate  of  iron). 

LIME  AND  AN  IRON  SALT. 

At  Ealing  the  lime  (20  cwt.  per  week 
to  3,000,000  gallons)  is  added  to  the  sew- 
age in  the  course  of  its  transit  to  the 
subsidence  tanks.  These  tanks,  each 
measuring  64  ft.  X  10  ft.  X  10  ft.  deep, 
are  divided  into  five  compartments  by 
cross  planks,  where  the  lime  precipitate 
subsides.  In  the  last  subdivision  of  the 
tanks,  the  defecated  sewage  is  treated 
with  an  iron  solution  (crude  sulphate  15 
cwt.  to  3,000,000  weekly).  The  sewage 
then  flows  upwards  through  two  filter 
beds  (No  1,  gravel,  30  ft.  X  10  ft.  X  2  ft. 
thick ;  No.  2,  sand,  60  ft.  X  10  ft.  x  2ft. 
thick),  the  effluent  being  clear  and  in- 
offensive when  discharged. 

At  Northampton,  in  1862,  lime  (as  milk 
of  lime)  and  chloride  of  iron  (in  solution) 


169 

were  usedjas  sewage  precipitants.  The 
constituents  were  mixed  together,  and 
so  decomposed,  before  they  were  added 
to  the  sewage  [60  Ibs.  of  solid  chloride 
of  iron,  12  bushels  of  lime  to  400,000 
gallons  of  sewage  daily].  There  was  no 
mechanical  contrivance  to  mix  the  sew- 
age with  the  chemicals.  The  sewage 
after  treatment  passed  into  two  subsid- 
ing tanks  (40  ft.  X  30  ft.  and  60  ft.  X  30 
ft.,  each  5  ft.  deep),  from  the  second  of 
which  it  flowed  over  a  weir  into  an  out- 
fall channel  a  mile  in  length,  being  ulti- 
mately discharged  into  the  River  Nene. 
The  tanks  were  worked  for  a  fortnight, 
when  the  sludge  was  conveyed  into  pits, 
and  mixed  with  the  town  refuse,  the 
manure  realizing  Is.  9d.  per  load. 

Letheby  recommended  adding  the  iron 
salt  to  the  sewage  first  and  the  lime  after- 
wards, and  that  some  mechanical  contri- 
vance for  stirring  the  treated  sewage  both 
after  the  addition  of  the  iron  and  the 
lime  should  be  adopted.  He  considered 
4.5  grains  of  chloride  of  iron  and  15  grains 
of  lime  per  gallon  was  needed.  These 


170 

details  were  adopted,  and  the  results 
obtained  were  excellent. 

Some  difficulty  having  occurred  in 
procuring  the  chloride  of  iron,  a  solution 
was  prepared  on  the  works  of  9.400 
grains  per  gallon.  A  fit  of  economy  then 
led  the  authorities  to  reduce  the  quantity 
to  0.006  grain  of  chloride  of  iron  and 
5.88  grains  of  lime  per  gallon,  quantities 
manifestly  insufficient,  under  which  treat- 
ment it  was  seen  and  reported  on  by  the 
Rivers  Pollution  Commissioners. 

For  a  short  period  combinations  of 
lime  and  salts  of  iron  were  used  both  at 
Clifton  and  Cheltenham. 


Having  now  dealt  with  the  various 
precipitants  suggested,  to  throw  down 
the  suspended  matter  and  coagulate  a 
part  of  the  dissolved  slimy  organic  mat- 
ter of  sewage,  let  me  note  that  these 
precipitants,  for  practical  purposes,  are 
lime,  chloride  of  magnesium,  sulphate  and 
phosphate  of  alumina,  and  salts  of  iron, 
alone  or  in  conjunction  with  each  other. 

In  addition   to  these,    clay  and  other 


171 

weighting  bodies,  together  with  charcoal 
and  other  absorbent  substances,  have 
been  added  under  various  patents. 

In  selecting  a  chemical  precipitant,  five 
main  points  present  themselves  to  us : 

1.  That,    consistently  with   purity    of 
effluent,  the   chemicals  used  should  be 
cheap. 

2.  That  the  precipitant  should  act  as 
a  deodorizer  and  disinfectant  as  well  as 
a  precipitant. 

3.  That     the     precipitated     matters 
should  subside  rapidly. 

4  That  the  maximum  purity  should 
be  obtained  with  the  minimum  of  deposit, 
in  other  words,  with  the  smallest  quantity 
possible  of  chemicals. 

5.  That  the  sludge  should  part  with 
its  water  readily. 

I  now  approach  the  really  practical 
question,  asked  all  over  the  country, 
from  every  sanitary  authority,  often  in 
tones  of  painful  despair,  viz.,  How  shall 
toe  deal  with  our  sewage  ? 

And  here  let  me  say  there  is  no  one 
answer  that  can  be  given  to  this  ques- 


172 

tion.  The  adviser,  to  advise  fairly,  must 
be  prepared  to  sink  his  hobby,  be  it  the 
hobby  of  precipitation  or  the  hobby  of 
irrigation,  remembering  that  whilst  con- 
ditions favorable  to  his  hobby  may 
exist  at  one  place,  conditions  abso- 
lutely unfavorable  may  exist  at  another. 
Further,  it  is  of  no  use  telling  how 
some  pet  plan,  say,  of  irrigation  or 
of  precipitation,-  has  succeeded  at  some 
one  place  or  another,  persuading  local 
authorities  to  undertake  a  pilgrimage  of 
inspection  (although  they  are  usually 
ready  enough  to  do  so),  and  arguing  that 
because  such  and  such  plan  has  succeeded 
at  A,  therefore  it  will  succeed  at  B. 
There  is  no  universal  remedy  for  the 
sewage  difficulty,  and  no  one  plan  of 
treatment  to  be  laid  down. 

When  people  say,  "  The  whole  thing  is 
easy  enough,  only  do  this  or  do  that,"  be 
certain  they  have  not  grasped  the  diffi- 
culties of  the  subject,  and,  I  fear,  know 
little  about  it. 

Let  me  attempt,  however,  to  suggest 
certain  fundamental  propositions  that 


173 

may  serve  as  a  starting  point  in  advising 
local  authorities : — 

1.  Towns  must  be  prepared  to  pay  to 
be  clean.     You  will  never  be  able  to  make 
your   sewage  pay   your   rates ; — on   the 
contrary,    experience     shows    that    you 
must  purify  your  sewage  at  the  expense 
of  the  rates. 

2.  That    health    demands   that   your 
sewage  should  be  got  rid  of,  and  purified 
at  any  cost.     Minimize  the  cost,  but  pay 
you  must  for   purification.     Hence  you 
must  be  prepared   not  only   to    borrow 
money  to  erect  works,  but  for  an  annual 
expenditure  after  the  works  have  been 
erected. 

3.  That  no  matter  how  perfect  your 
works,  your  sewage  will  require  constant 
attention,  Sunday  as  well   as  week-day, 
night  as  well  as  day. 

4.  That  to  let  unpurified  sewage  pass 
into  a  stream  means  passing  your  filth 
on  to  your  neighbors.     Sewage  ought  to 
be   treated    where   the   sewage   is   pro- 
duced, as   far    as    it   is   possible.     And 
considering  this  aspect  of  the  subject,  let 


174 

me  add,  litigation  is  a  more  expensive 
luxury  than  sewage  treatment,  and 
breeds,  if  possible  (although  on  this  I 
admit  a  doubt),  more  ill-will. 

5.  That  although  our  duty  is  to  do  our 
work  well,  at  as  small  a  cost  as  possible, 
we  neither  require  (qua  the  effluent)  to 
produce  a  drinking  water,  nor  (qua  the 
sludge)  to  produce  Peruvian  guano. 

Our  sewage  has  to  be  treated.  We 
shall  necessarily  inquire  how  much  sew- 
age there  is  to  treat,  and  what  kind  of 
sewage  it  is. 

Let  me  suppose  that  our  first  thought 
is  the  possibility  of  an  irrigation  scheme. 

Far  be  it  from  me  to  say  that  irriga- 
tion may  not  prove  successful.  But  it  is 
fair  to  note  that,  to  attain  the  end  of  a 
sanitary  authority,  experience  has  shown 
that  the  sanitary  authority  must  itself  be 
the  proprietor  of  the  land.  If  you  give 
the  sewage  to  the  farmers  (supposing 
they  would  accept  your  gift)  the  interests 
of  the  local  authority  and  of  the  farmers 
are  opposite.  For  it  is  manifest  that  the 


175 

interest  of  the  farmer  is  his  crops,  whilst 
the  interest  of  the  local  authority  is  the 
purification  of  their  sewage.  The  local 
authority,  as  a  sanitary  authority,  must 
demand  a  pure  effluent  at  all  times,  in 
winter  and  in  wet  seasons  as  well  as  in 
summer  and  in  dry  seasons.  Between 
these  divided  interests  of  farmer  and 
sanitary  authority,  the  question  of  purity 
of  effluent  may,  and  in  our  experience 
usually  does,  fall  to  the  ground.  Hence, 
if  irrigation  is  to  be  adopted,  the  local 
authority  must  provide  its  own  land  for 
the  purpose. 

Sundry  questions  at  once  arise : — 
1.  Is  it  practicable  to  obtain  sufficient 
land,  and  land  properly  constituted  as  re- 
gards general  character,  level,  etc.,  for 
irrigation  purposes'?  Let  me  note  that 
the  word  "  sufficient "  is  not  capable  of 
precise  definition.  What  is  sufficient  in 
the  case  of  one  kind  of  land  is  in- 
sufficient in  the  case  of  another.  What 
is  sufficient  land  with  one  kind  of  engi- 
neering treatment,  and  with  one  kind  of 
sewage,  would  prove  insufficient  with 


176 

another  kind   of   engineering  treatment 
and  another  kind  of  sewage. 

2.  Is    this   properly    constituted   land 
reasonably  near  to  the  town,  so  that  the 
cost  of  conveying  the  sewage  to  the  land 
will  not  be  excessive,  but  at  the  same 
time  reasonably  distant,  so  that  the  town 
may  not  derive  injury  from  the  nuisance 
likely  (we  might  almost  say  certain)  at 
times  to  result? 

3.  Is   the  land  of  such  a  level  as   to 
necessitate  pumping  ?     Is  it  near  a  water- 
course, canal,  railway,  etc.  ? 

Let  me  suppose  these  questions  an- 
swered satisfactorily.  A  very  serious 
further  question  has  now  to  be  con- 
sidered, viz.,  where  is  the  effluent  to  be 
discharged  ? 

The  importance  of  the  question  is  this. 
In  all  irrigation  schemes,  of  whatever 
nature,  we  are  dependent  for  effective 
purification,  on  effective  land,  in  effective 
order.  The  action  of  land  may  become 
ineffective  from  circumstances  over  which 
we  have  no  control,  viz.,  frost,  where  the 
ground  may  become  absolutely  impene- 


177 

trable,  and  water -logging,  in  times  of 
heavy  rains,  when  the  sewage  is  in  far 
•  greater  quantity  than  normal,  and  for  a 
time  at  least  more  foul  than  normal,  from 
flushing  of  the  sewers. 

Hence,  if  the  outfall  is  into  a  river 
where  considerable  purity,  and  unfailing 
continuity  of  purity,  is  demanded,  an 
irrigation  scheme  is,  to  say  the  least,  un- 
safe. If,  however,  the  discharge  be  into 
the  sea,  or  into  a  tidal  estuary,  or  into  a 
stream  where  the  occasional  discharge  of 
a  little  doubtful  water  is  unimportant,  an 
irrigation  scheme,  pure  and  simple,  may 
pass  muster. 

To  secure  land  for  a  sewage  farm  (even 
after  the  proper  land  has  been  found)  is 
not  an  easy  matter.  It  often  means  a 
fancy  price.  It  means,  too,  a  mass  of 
opposition  from  adjoining  property  hold- 
ers, who  suddenly  discover  that  all  the 
fields  in  the  vicinity  of  the  land  selected 
are  building  ground. 

I  do  not  mean  this  as  an  objection 
peculiar  to  land  required  for  irrigation 
purposes. 


178 

Another  matter  has  to  be  considered. 
If  land  be  taken  on  lease  for  a  sewage 
farm,   its   renewal    may   prove   difficult.  - 
The  lease  of  the  Croydon   farm  expires 
in  1892. 

I  will  at  once  admit  that  my  own  ex- 
perience has  led  me  to  the  opinion  that 
greater  advantages  result  from  a  com- 
bined process  of  precipitation  and  irriga- 
tion than  can  be  obtained  by  either 
method  independently,  admitting  as  I  do 
to  the  full,  that  a  good  effluent  may  be 
obtained  by  a  precipitation  process  alone, 
nearly  as  good,  in  fact,  as  any  effluent 
that  can  be  obtained  by  irrigation.  A 
precipitation  scheme  by  itself  has  these 
two  enormous  advantages  over  irriga- 
tion, viz.  (1)  its  efficient  working  is  totally 
independent  of  weather,  and  (2)  that,  if 
sufficiently  large  works  be  erected,  any 
emergency  of  quantity  can  be  met.  Pre- 
cipitation has  had  its  greatest  enemies  in 
its  most  earnest  advocates.  Extravagant 
advantages  have  been  claimed  for  it.  The 
sludge  has  been  advertised  as  of  enor- 
mous manurial  value.  Patents  by  the 


179 

hundred  have  been  taken  out.  Precipi- 
tation advocates  have  been  for  the  most 
part  advocates  of  a  system  in  which  they 
are  interested.  And  there  is  no  wonder 
that  distrust  in  precipitation  schemes 
have  arisen,  when  the  claims  put  forth 
by  enthusiasts  and  patent-mongers  have 
been  weighed  in  the  balance  against  the 
facts,  and  found  wanting. 


Supposing,  then,  we  determine  on  a 
precipitation  process,  there  arises  the 
first  £freat  question,  what  precipitant 
shall  be  used  f  Here  two  points  must  be 
considered.  At  any  rate  it  will  not  be 
disputed : — 

1.  That,    consistently   with   efficiency 
and    purity   of    effluent,    the    chemicals 
should  be  cheap. 

2.  That  the  smallest  quantity  of  chemi- 
cals that  experience  proves  is  capable  of 
doing  the  work  properly  should  be  added 
to   the   sewage,   so   as  to  minimize  the 
quantity  of  sludge  formed. 

I  am  anxious  to  be  in  no  sense  the 
advocate  of  any  one  system  of  precipita- 


180 

tion.  I  will  admit,  however — the  process 
now  is  not  a  patent,  and  if  it  were  I 
should  speak  with  greater  caution — that 
the  ABC  turns  out  the  best  effluent 
with  which  I  am  acquainted.  My  own 
experience  leads  me  to  speak  very  highly 
indeed  of  the  combined  use  of  lime  and 
sulphate  of  alumina.  The  quantity  of 
lime  which  is  to  be  added  first  should  be 
such  as  to  render  the  sewage  faintly 
alkaline.  Probably  at  the  rate  of  from 
five  to  seven  grains  per  gallon  will  be 
needed  for  this  purpose.  It  should  be 
added  as  milk  of  lime,  and  should  be 
thoroughly  stirred  in  by  means  of  a 
paddle-wheel,  or  other  efficient  mixer.  A 
flow  of  a  few  yards  should  now  be  allowed, 
to  permit  the  aggregation  of  the  precipi- 
tate. This  having  taken  place,  a  solution 
of  crude  sulphate  of  alumina,  in  the 
proportion  of  about  five  grains  of  sul- 
phate of  alumnia,  is  to  be  added,  and  the 
sewage  again  actively  stirred.  In  the 
alkaline  condition  of  the  sewage,  the 
alumina  will  be  precipitated,  and  will 
then  combine  with  a  portion  of  the 


181 

organic  matter,  forming  together  an  in- 
'soluble  precipitate.  Thus  treated,  the 
sewage  should  be  allowed  to  flow  into 
tanks  for  the  precipitated  matters  to  col- 
lect. 

Let  me  attempt  to  indicate  the  effects 
of.  such  treatment.  A  portion  of  the 
lime  will  be  at  once  converted  into  car- 
bonate of  lime,  by  combining  with  the 
carbonic  acid  present  in  the  sewage,  and 
serve  as  a  weighting  material  to  aid  in 
the  deposition  of  the  lighter  flocculent 
materials.  This  mechanical  action  of  the 
lime  carbonate  is  of  great  importance. 
The  flocculent  suspended  matter  is  no 
doubt  one  of  the  most  important  materi- 
als to  remove,  because  it  is  that  ingredi- 
ent of  the  sewage  which  readily  putrefies, 
and  in  this  way  causes  a  nuisance.  It  is, 
moreover,  so  light  that,  unless  weighted, 
it  is  difficult  to  precipitate.  A  second 
portion  of  the  lime  combines  with  some 
of  the  organic  matter  in  solution,  pro- 
ducing an  insoluble  precipitate  (of  un- 
certain composition)  of  a  compound  of 
lime  an$  organic  matter,  the  subsidence 


182 

of  which  is  again  assisted  by  the  forma- 
tion of  the  carbonate  of  lime  previously 
described.  A  third  portion  of  the  lirne 
renders  the  sewage  slightly  alkaline. 

The  alumina  salt  is  now  to  be  added. 
The  alumina  is  precipitated,  owing  to  the 
alkalinity  effected  by  the  slight  excess  of 
lime.  This  alumina  combines  with  some 
of  the  organic  matter  in  solution,  not 
precipitated  by  the  action  of  the  lime. 
The  power  of  alumina  in  combining  with 
dissolved  organic  matter,  and  so  remov- 
ing it  from  solution,  is  taken  advantage 
of  in  many  commercial  processes. 

Respecting  the  iron  salts,  one  strong 
objection  to  their  use  is,  that  if  the 
effluent  be  discharged  into  a  river,  the 
stream  is  liable  to  be  blackened  from  the 
formation  of  a  sulphide  of  iron,  a  condi- 
tion likely  to  be  mistaken  by  the  general 
public  for  a  sewage  deposit.  I  have, 
therefore,  of  late,  admitting  the  value 
of  iron  compounds  as  precipitants,  hesi- 
tated to  recommend  their  use,  save  under 
very  .exceptional  circumstances.  As  re- 
gards the  use  of  phosphates  as  precipi- 


183 

tants,  the  effluent  is  almost  certain  to 
contain  some  phosphoric  acid,  which 
greatly  aids  the  growth  of  low  forms  of 
fungoid  growths,  amongst  which  may  be 
included  the  so-called  sewage  fungus. 

It  is  advisable  that  the  effluent,  before 
its  discharge  into  a  stream,  be  at  least 
neutral  and  preferably  slightly  acid. 
This  condition  is  easily  brought  about 
by  the  addition  of  a  small  quantity  of 
acid  to  the  effluent  before  its  escape. 

The  effluent,  after  treatment,  will  no 
doubt  have  a  slight  odor.  This  is  not, 
however,  a  sewage  smell.  If  in  this  con- 
dition of  comparative  purity — indicated 
by  absence  of  color  and  freedom  from 
suspended  matter — it  be  allowed  to  flow 
over  and  through  a  small  area  of  land  (a 
loamy  sand  or  gravel  by  preference)  to 
serve  as  a  chemical  filter,  high  degree  of 
purity  may  be  obtained,  and  the  finer 
finishing  touches  of  purification  effected. 

The  evils  of  irrigation  under  such  cir- 
cumstances do  not  arise.  Such  a  filtra- 
tion of  the  effluent  (1)  cannot  produce  a 
nuisance,  because  it  contains  no  foul  sus- 


184 

pended  matters  to  collect  on  the  surface 
and  putrefy ;  (2)  it  cannot  clog  the 
ground  because  the  gelatinous  and  papier 
mac/ie  matters  in  solution  have  been  re- 
moved ;  whilst  (3)  it  has  a  certain  manu- 
rial  value,  the  quantity  of  ammonia  in 
solution  being  not  much  less  than  that  of 
the  original  sewage. 

Again  I  may  quote  from  Dr.  Monro's 
paper,  who,  it  will  be  remembered,  doubts 
the  advisability  of  ordinary  irrigation  as 
a  general  process,  on  account  of  imper- 
vious deposits  choking  the  pores  of  the 
land.  He  says,  "The  removal  of  the 
suspended  matter,  however,  from  the 
sewage,  renders  irrigation  much  more 
practicable.  With  a  clear  effluent  and  a 
porous  soil,  the  nitrifying  power  brought 
into  play  is  enormous,  and  a  moderate 
area  of  soil,  whether  of  grass  land  or 
arable,  can  deal  with  large  and  almost 
continuous  doses  of  sewage  water.''  Dr. 
Monro  points  out  that  the  presence  of 
objectionable  organic  matter  is  as  destruc- 
tive to  nitrification  as  the  clogging  of  the 
pores  of  the  soil,  or  a  great  lowering 
of  temperature. 


185 

The  following  table  will  give  some 
idea  of  the  cost  of  chemical  treatment  of 
water-carried  sewage. 

I  may  be  asked  what  quantity  of  land 
is  needed  where  sewage  has  been  effi- 
ciently precipitated.  Again  the  answer 
will  depend  on  the  nature  of  the  land. 
But  if  I  say  an  acre  to  every  5,000  to 
7,000  people.  I  am  well  within  the  results 
of  my  experience. 

Sewage  works  of  the  kind  I  have  men- 
tioned can  be  carried  out  without  the 
slightest  nuisance.  The  mixing  should 
be  done  in  closed  wells.  The  mixture,  as 
it  flows  into  the  tanks,  should,  if  suffi- 
cient chemicals  have  been  used,  be  as 
free  from  odor,  at  the  distance  of  a  few 
feet  from  the  mixer,  as  common  water. 
The  land  cannot  possibly  produce  noxious 
effluvia  or  poisonous  vapors,  because  the 
sewage  has  already  been  treated  with 
antiseptic  precipitants. 

Of  course  all  depends  on  the  treatment 
having  been  efficient.  Success  in  the 
treatment  of  sewage  obeys  the  same 
laws  in  this  respect  as  success  in  any- 
thing else. 


186 


•0?a  'saiAUd  Sai 

-A^dxua  pxre  STIJO 
-ixuaxp  aoj  'xre  aad 
pisau;  uad  !}soo  -^ox 

g             » 

•dS    ®       X    S 

From  the  above  table  it  will  be  seen  that  if  the  proportion  of  water  closets  at  Bradford  and  Leeds  was  larger,  the  cost 
of  chemicals  at  the  outfall  must  be  considerably  increased.  If  on  the  other  hand  the  proportion  of  water  closets  at  Cov- 
entry was  as  low  as  it  is  at  Bradford  and  Leeds,  the  cost  of  chemicals  could  be  considerably  reduced,  and  would  probably 
not  exceed  8s.  or  9s.  per  million  gallons.  From  this  it  will  be  seen  that  alumina  treatment,  such  as  that  employed  at  Cov- 
entry, is  cheaper  than  lime  treatment  ;  and  it  has  already  been  shown  by  official  investigations,  that  lime  treatment  and 
its  modiflcations  are  not  as  efficient  as,  or  equal  in  sanitary  results  to,  alumina  treatment.  It  is,  moreover,  still  more 
expensive  than  is  shown  in  this  table,  because  of  the  fact  that  it  produces  twice  the  quantity  of  sludge  as  alumina  treat*— 
ment  does,  the  dealing  with  and  disposal  of  which  is  a  very  costly  matter,  particularly  as  it  is  practically  useless  as  a 
manure,  and  not  so  readily  saleable  as  that  produced  by  alumina  treatment. 

•o^a  'saiAUd  Sm 
-Adxua  aoj  xunuxTB 
J8(d  puau;  ,iad  IJSOQ 

^   ^ 

TJco     o         ^     S^ 

•spjoiraaxp  aoj     } 
uinuuia  aad        he  rfv                        -K 
pi?axj  ,iad  ;SOQ      | 

•sreoixuaxjQ 
aoj  suoip3£) 
uoiiUK  -rad  ^SOQ 

•0        CO              0        05 
T3*H 

t»S    S       ^    S 

•o^a  'suappiui 
'saiAUd  SuiAdraa 
jo  isoo  p3hxiuy 

TH"      ^            Qtf      Of 

•o;a 
'snappiui  'satALid 
mojj  ^jBai; 
paAOiuaa  asnj 
-aa  jo  ^!ji!juBn5 

n       so           DO       cc 
i>      t>T         10      g" 

•asn  xn  '-o^a  'snap 
-puu  jo  satAud 
jo  aaquin^j 

^i 

s  s     1  i 

ft       CO 

§  " 

•asu  ui 
siasop  aa^-BM 
jo  jaqranNi 

i  * 
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^    b     "2    « 
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1  !    1  J 

00         « 

Name  of  Process. 

Alumina,  iron,  etc.  .  . 
Alumina,  iron,  etc.^| 
sewagre  if  dye  > 
were  absent.  .  ) 
Precipitation  by  1 
Lime  and  Coke  V 
Filtration  J 
Lime  process  

187 

I  am  desirous  here  of  pointing  out 
certain  details  of  treatment  essential  for 
the  success  of  a  precipitation  process : — 

1.  It  is  necessary  that  the  sewage 
treated  should  be  fresh — by  which  I 
mean  sewage  in  which  active  putrefactive 
changes  have  not  taken  place.  Perhaps, 
speaking  generally,  the  sewage  should 
not  be  more  than  48  hours  old  for  effect- 
ive precipitation.  But  it  is  certain  that, 
with  a  sewage  of  not  more  than  24 
hours  old,  a  far  better  result,  with  a 
smaller  amount  of  chemicals,  can  be 
obtained.  In  fixing,  however,  the  time, 
a  certain  elasticity  must  be  allowed,  an 
elasticity  by  way  of  extension  in  winter 
and  of  compression  in  summer.  I  have 
said  the  'treatment  should  be  effected 
before  active  putrefaction  commences. 
In  sewage,  the  decomposition  of  the 
different  constituents  takes  place  at 
different  times,  in  some  cases  the  periods 
of  active  change  being  separated  by 
periods  of  practical  rest.  Thus  a  certain 
alteration  in  sewage  takes  place  almost 
immediately.  This  results  (amongst 


188 

other  changes)  in  the  breaking  up  of 
the  urea,  and  the  formation  from  it  of 
carbonate  of  ammonia.  It  is  a  rare  thing 
indeed  for  any  sewage,  when  it  reaches 
the  sewage  works,  to  contain  more  than 
a  trace  of  urea.  No  nuisance  results 
from  this  change  of  the  urea.  A  con- 
siderable interval  occurs  before  any  other 
putrefactive  stage  occurs,  and  it  is  during 
this  interval  when  the  precipitation  should 
be  effected.  If  this  period  be  allowed  to 
pass,  increased  difficulty  in  working  re- 
sults. 

2.  The  straining  of  the  sewage  before 
treatment,  in  order  to  remove  rags,  corks, 
and  the  various  et  ceteras,  such  as  dead 
rats,  walking  sticks,  etc.,  that  come  down 
along  with  the  sewage,  is  advisable  but 
not  essential,  in  order  to  prevent  accumu- 
lations on  the  surface  of  the  tanks. 
Fixed  wire  gratings  are  objectionable,  on 
the  ground  of  their  becoming  so  easily 
choked.  Baldwin  Latham's  extractor  is 
employed  in  several  places  with  success. 

3.  It  is  essential  that  sufficient  chemi- 
cals be  employed  to  effect  complete  pre- 


189 

cipitation,  disinfection,  and  deodorization 
of  the  sewage. 

No  greater  mistake  can  be  committed 
than  to  starve  the  chemicals.  To  this 
must  be  attributed  many  cases  where  a 
precipitation  process  has  proved  a  failure. 
A  local  authority  will  spend  a  large  sum 
in  erecting  works,  perfect  in  architectural 
detail,  excellent  for  sewage  treatment, 
whilst  they  shirk  a  small  annual  payment 
for  the  necessary  chemicals.  I  need 
scarcely  point  out  that  efficient  works 
will  not  purify  sewage.  They  are  but 
the  means  to  an  end.  It  is  better  to 
calculate  the  amount  of  chemicals  to  be 
used  on  the  population  than  on  the 
quantity  of  sewage. 

4.  It  is  essential  that  after  the  chemi- 
cals are  added,  the  mixture  should  be 
well  stirred.  The  chemist  understands 
the  value  of  the  stirring  rod  in  order  to 
effect  perfect  chemical  contact.  My  own 
experience  is  that  the  chemicals  added  to 
sewage  are  often  wasted  from  insufficient 
stirring.  Not  only  is  it  the  case  that 
they  do  not  precipitate  so  much  as  they 


190 

might,  but  the  process  of  flocculation  is 
imperfect,  and  the  difficulty  of  obtaining 
a  clear  effluent  correspondingly  great. 

5.  It  is  essential  that  there  should  be 
sufficient  tank  accommodation.  Let  me 
note  sufficiency  of  tank  accommodation  is 
necessary  for  two  reasons — (1)  That  the 
precipitate  may  subside  perfectly,  and 
leave  a  clear  colorless  effluent.  Shallow 
tanks,  with  considerable  velocity  of  sew- 
age through  them,  or  insufficient  tank 
accommodation,  means  imperfect  subsi- 
dence. Imperfect  subsidence  means  the 
discharge  of  a  certain  quantity  of  floccu- 
lent  organic  matter  in  the  effluent  (the 
mineral  matter  being  more  likely  to  be 
deposited  from  its  greater  specific  gravity), 
and  which  flocculent  matter  is  likely  to 
occasion  nuisance  from  its  decomposi- 
tion. The  treated  sewage  should  flow 
through  at  least  two  subsiding  tanks  in 
series,  the  first  being  capable  of  holding 
one  hour's  flow,  and  the  second  not  less 
than  four  hours'  flow.  The  tanks  should 
be  at  least  four  feet  deep,  and  the  over- 
flow of  the  defecated  sewage  should  be 


191 

over  a  weir,  not  more  than  an  inch  below 
the  surface.  There  should  be  a  double 
set  of  tanks  for  successful  working. 

(2)  Sufficiency  of  tank  accommodation 
is  also  important,  so  that  the  sludge  may 
be  frequently  removed,  otherwise  the 
freshly  precipitated  sewage  may  be  con- 
taminated by  the  decomposing  materials 
of  a  previous  precipitation,  or  a  nuisance 
result  from  a  collection  of  decomposing 
matter.  Many  a  good  effluent  is  spoilt 
by  foul  materials  being  allowed  to  collect 
in  the  subsiding  tanks.  These  materials 
undergo  putrefaction,  the  gases  given  off 
contaminating  the  effluent.  The  solid 
matters,  becoming  specifically  lighter 
than  the  liquid  by  the  gases  of  putrefac- 
tion developed  in  and  amongst  them,  rise 
to  the  surface,  the  floating  black  masses 
presenting  an  objectionable  appearance, 
and  discharging  offensive  products  into 
the  air.  After  a  time  these  black  masses 
sink,  and  thus,  by  constant  commotion 
of  the  precipitated  matters,  a  turbid 
effluent,  with  a  more  or  less  foul  smell, 
results. 


192 

6.  That   the   defecated   water   should 
flow  through  a  shallow  open  conduit  of 
not  less  than  a  quarter  of  a  mile  before 
being  discharged  into  the  stream. 

7.  The  stream  into  which  the  effluent 
is   discharged    should  have  a   free   run, 
and  in  volume  be  not  less  than  eight  times 
the  volume  of  the  defecated  sewage. 

8.  That  the  tanks  themselves   should 
not  only  be  emptied  of  the  sludge,  but 
thoroughly   cleansed    before    being    re- 
filled. 

The  extent  of  tank  accommodation 
needful  will  depend  a  good  deal  on  the 
dilution  of  the  sewage  to  be  dealt  with, 
either  by  subsoil  or  surface  waters,  or  by 
both,  and  whether  the  treatment  em- 
ployed be  intermittent  or  continuous. 
The  following  gives  the  tank  capacity 
provided  at  certain  successful  works : — 


193 


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194 

The  most  suitable  depth  for  tanks  is 
from  5  to  6  feet. 

It  may  be  worth  noting  the  rate  at 
which  the  precipitated  matters  deposit 
when  the  treatment  with  lime  and  sul- 
phate of  alumina  is  efficient,  and  the 
sewage  collected  in  tanks  of  5  feet  6 
inches.  The  water  begins  to  clear  a  few 
minutes  after  the  cessation  of  agitation. 
In  thirty  minutes  it  clears  to  a  depth 
of  3  feet,  with  8  inches  precipitate, 
while  after  two  hours  the  precipitate 
will  measure  4|  inches  only. 

All  this  accomplished,  two  questions 
remain:  (1.)  Have  you  produced  such 
an  effluent  that  it  will  not  pollute  the 
watercourses'?  (2.)  Is  not  the  sludge 
certain  to  cause  a  nuisance1?' 

That  a  clear,  colorless,  non- fro  thing 
effluent  can  be  produced  by  mere  chemi- 
cal precipitation,  is  not  a  matter  of  opin- 
ion, but  of  fact.  That  an  effluent  abso- 
lutely without  smell  can  be  produced,  I 
doubt.  The  smell,  however,  of  the  efflu- 
ent from  properly  treated  sewage  is  not 
the  odor  of  sewage.  I  have  never,  I  can- 


195 

didly  confess,  found  an  effluent  without 
a  certain  smell.  I  have  heard  a  well- 
known  authority  ascribe  it  to  the  pres- 
ence of  minute  traces  of  essential  oils  or 
strong  smelling  bodies  (e.g.,  onions),  dif- 
ficult of  removal  by  precipitants.  If  the 
effluent  is  to  be  discharged  into  the  sea, 
or  into  a  tidal  or  large  river  (say  200  or 
300  times  the  volume  of  the  effluent), 
this  odor  is  absolutely  immaterial ;  but 
where  great  purity  is  required,  e.g.,  when 
the  effluent  has  to  be  discharged  into  a 
small  stream  or  into  a  river  employed  at 
a  short  distance  from  the  outfall  for 
drinking  purposes,  some  further  treat- 
ment is  called  for. 

Such  further  treatment  consists  either 
(1)  in  the  use  of  artificially  prepared  fil- 
ter beds,  such  as  are  used  for  the  filtra- 
tion of  water,  or  (2)  by  filtration  through 
a  small  area  of  land. 

Of  these  two  methods,  I  prefer  the 
latter.  After  careful  consideration,  I  con- 
sider that  for  this  purpose  an  acre  to 
every  5,000  to  7,000  people  (as  I  have 
before  noted)  is  abundant.  I  shall  not 


196 

discuss  any  question  of  manurial  value, 
although  I  may  point  out  that  the  am- 
monia of  sewage  is  not  appreciably  af- 
fected by  ordinary  chemical  precipitants. 
(2.)  Is  not  the  sludge  an  inevitable 
cause  of  nuisance?  I  confess  it  may  be, 
and  often  has  been.  Allowing  the  sludge 
to  accumulate  week  after  week  in  the  de- 
positing tanks,  is  not  only  an  evil  (as  I 
have  pointed  out)  so  far  as  our  endeav- 
ors to  procure  a  good  effluent  is  con- 
cerned, but  an  unmitigated  nuisance,  so 
far  as  relates  to  the  sludge.  Further, 
the  old  method  of  emptying  the  sludge 
into  open  sludge  pits,  where  the  liquid 
portion  was  allowed  to  drain  away  and  to 
evaporate,  has  proved  a  constant  cause 
of  just  complaint,  more  especially  in  warm 
weather.  I  am  not  sure  whether  the 
sludge,  under  these  conditions,  was  not 
sometimes  a  greater  nuisance  after  being 
taken  out  of  the  sewage  than  when  left 
in  it.  Until  lately  the  difficulty  of  the 
disposal  of  the  sludge  was  one  inherent 
to  all  precipitation  works.  Until  lately 
I  said— because  now  the  difficulty  is  over- 
come. 


197 

It  is  essential,  both  in  the  interests  of 
the  effluent  and  of  the  sludge,  that  it 
should  be  frequently  removed  from  the 
tanks — I  mean  that  the  sludge  should  be 
removed  before  putrefactive  decomposi- 
tion sets  in.  This  frequent  removal  is 
necessary  (1)  so  that  the  effluent  may  not 
be  polluted,  and  (2)  so  that  no  nuisance 
may  result  during  the  removal  of  the 
sludge  and  the  cleansing  of  the  tank. 
For  here  I  must  express  a  strong  opinion 
that  it  is  not  enough  merely  to  empty 
the  tank  of  sludge,  but  it  is  imperative 
that,  after  being  emptied,  and  before 
being  refilled,  the  tank  should  be  well 
cleansed — in  other  words,  that  the  mat- 
ters which  stick  to  the  sides  of  the  tank 
should  be  completely  and  efficiently  re- 
moved to  prevent  nuisance  or  fouling  by 
subsequent  decomposition. 

It  would  be  outside  my  province  to 
deal  with  the  methods  of  raising  the 
sludge  out  of  the  tanks.  This  is  a  purely 
mechanical  question.  The  sludge  is  a 
thick  black  liquid,  which  may  be  pumped 
out  of  the  tanks  or  lifted  out  by  bucket 


198 

pumps  into  troughs,  which  serve  to  con- 
vey it  wherever  it  may  be  wanted. 

I  am  indebted  for  the  table  on  page  199 
to  the  manager  of  a  sewage  works  in  a 
residential  neighborhood  of  a  population 
of  18,000.  The  process  used  is  lime  and 
sulphate  of  alumina.  The  sewage  is 
pressed  in  one  of  Johnson's  presses  : 

The  record  of  sludge  begins  on  Feb- 
ruary 16, 1885,  and  ends  on  February  16, 
1886.  The  wet  sludge  is  got  by  a  series 
of  eighty  different  actual  measurements 
on  various  days  throughout  the  year. 
The  pressed  sludge  is  got  by  keeping 
a  record  of  the  number  of  times  the 
presses  were  emptied  on  every  day  in  the 
year.  A  cubic  yard  of  wet  sludge  is 
taken  as  weighing  .98  of  a  ton,  and  a 
cubic  yard  of  pressed  sludge  as  weighing 
.75  of  a  ton  (actual  determinations). 

The  following  details  are  taken  from 
Mr.  Lacey's  report  to  the  Brentford 
Local  Board,  on  "  The  Disposal  of  Sew- 
age Sludge."  (See  page  200.) 


199 


• 


0 

t> 

O 


3   O   co   bD  d 

:£  d  c8  g 

3S   o   {S  *5 


1  s* 

§  ^ 

a  ss 

<i  P« 


1C        "^ 
CO         O 


bO 

53 


200 


£ 

I 

71 

P 

O 


% 


OQ 


8§ 
^.5     o  . 

sill 
Isf 


frpl 

.  ^Ss-e 

"  3'aflS 

-u  fl  B 

«*r!  a?  >  O 
®-  &S  *5 

H^O  at 


201 

It  will  be  convenient  at  this  point  to 
consider  the  amount  of  sludge  pro- 
duced, its  value  as  a  manurial  agent, 
and  the  method  suggested  for  its  dis- 
posal. 

I. — AMOUNT  OF  SLUDGE. 

The  quantity  of  sludge  varies  enor- 
mously, according  to  the  amount  of 
sewage,  and  the  precipitants  employed. 
Thus,  at  Coventry  the  sludge  from 
1,000,000  gallons  is  about  12.5  tons, 
whereas  at  Birmingham  it  varies  from  25 
to  33  tons. 

The  quantity  of  sludge  produced  from 
a  given  quantity  of  sewage  will  vary  ac- 
cording to  local  circumstances  and  con- 
ditions ;  such  for  instance  as  the  charac- 
ter of  the  soil,  the  condition  of  the  streets 
and  roads,  whether  surface  water  be 
wholly  or  in  part  admitted  to  or  excluded 
from  the  sewers,  whether  manufacturing 
refuse  is  included  in  the  sewage  to  be 
treated,  whether  or  no  the  w.  c.  be  in 
general  use,  and  whether  the  process  of 
precipitation  be  complete  and  efficient  or 
only  partial. 


202 

In  a  town  where  w.c.'s  are  in  general 
use,  where  the  soil  is  of  gravel  and  sand, 
where  surface  water  is  partially  admitted 
into  the  sewers,  where  there  are  no 
manufactories,  and  where  precipitation 
is  well  and  efficiently  done  with  chemicals 
of  modern  bulk,  the  proportion  of  pressed 
sludge  containing  50  per  cent,  of  moist- 
ure, may  be  taken  at  .6  (six  tenths)  of  a 
pound  per  head  per  day,  or  about  2  tons, 
14  cwt,  daily  per  10,000  of  the  population. 

The  principle  is  right: — Consistent 
with  efficiency,  produce  as  little  sludge 
as  practicable ;  and  this  for  two  reasons 
— (1)  that  if  it  has  any  value,  you  secure 
its  maximum  value ;  whilst  (2)  if  it  has 
no  value,  you  have  the  less  to  get  rid  of. 
Thus  with  some  precipitants  you  get  a 
large  volume  of  valueless  sludge.  With 
sulphate  of  alumina  you  get  comparatively 
little  sludge,  but  a  material  of  greater 
value.  Of  course  it  may  be  argued  that 
the  more  sludge  you  obtain,  the  more 
perfect  has  been  the  removal  of  the  im- 
purities of  the  sewage.  This  may  or 
may  not  be  true. 


203 

II. — COMPOSITION  AND  VALUE  OF  SLUDGE. 

I  am  anxious  at  once  to  say  that  I 
place  no  intrinsic  value  on  the  sludge 
whatsoever.  An  estimate  of  the  value  of 
sludge  from  different  places  has  been 
given  on  high  authority,  but  it  is  better 
to  regard  the  sludge  as  a  thing  to  be  got 
rid  of,  and  as  a  thing  which,  to  be  got  rid 
of,  must  cost  money  and  may  not  bring 
money.  The  following  table  of  the 
analyses  of  sludge  from  various  places, 
and  by  various  methods  of  precipitation, 
have  been  given  by  Dr.  Wallace  as  fol- 
lows: 


204 


os  ic  co1^ 


.as 
34 


e- 
ri£ 

w  i 


O  O?  TH  OJ  TH  TH  f>  OJ  O  CO  CO 

r)J         Oi  <N  p  TH  1C  CO  TO  TO  TO         TO 


CO       <N  »O  »O  (M  00  rf  -i-i  Tf  O 
O        QO  i>  i-l  Tt<  CO  CO  CO  O  CD 


0 
<N 


O 

s 


-2.S 


O        OOOi       iOCO 

.  > 


s  g 


8lOOTt<TOOCDTHOSO 
t^-QOCOlCOSCDTHTfiOO 

00        TO      '      '  O  CO  TH  OJ  TO  TH        O 

TO  TH  TH  Oi  O 


OS         TH          Ot 

Sl.a- a 


OS         THJ>T 


o 

PQ 


<N       1C  ( 


(NO?    I   (M       COCOTO       TH 


To 


ss  of  P 
tation. 


§  : 

Jj     • 
^^ 


Phosphate  of  lime 
Nitrogen 
Equal  to  ammonia 
Calculated  value 
per  ton 


205 


A  table  by  Dr.  Voelcker  on  the  esti- 
mated and  market  values  of  one  ton  of 
sludge  from  places  stated  is  here  given  : 

ESTIMATED  AND  MARKET  VALUES  OF  ONE  TON 
OF  SLUDGE  FROM  PLACES  STATED  (VOELCKER). 


Esti- 
mated or 
theoreti- 
cal 
value.* 

Practical 
or  market 
value.t 

1.  Bolton  sludge  (M  and  C 
process)               

£   s.    d. 
0    9    8V£ 

s.  d.       s.  d. 
3    3  to    4  10 

2.  Bolton  sludge,  15  per  cent, 
of  moisture 

111 

7    0  to  10    6 

3.  Bradford    sludge    before 
lime  was  added  
4.  Bradford  sludge  with   15 
per  cent,  of  moisture  .  .  . 
5.  Bradford     sludge      after 
treatment  with  lime  
6.  Bradford  sludge  with  15 
per  cent,  of  moisture.  .  . 
7.  Aylesbury,  ABC  sludge.. 
8.  Aylesbury,  ABC  sludge 
with    15    per   cent,    of 
moisture 

o  11  0*4 

0  19    3 
048 

1    0    0^6 
084^ 

0  16    8% 

3    8  to    5    6 
6    5  to    9    6 
1    6  to    2    4 

6    8  to  10    0 
2    9  to    4    2 

5    6  to    8    4 

9.  Coventry  sludge  of  Gen- 
eral Sewage  Manure  Co. 
11.  Rochdale  Manure.. 

0  16    9J4 
0  15  11>$ 

5    6  to    8    4 
5    4  to   8    0 

12.  Halifax  manure  by  Goux's 
process  

0  17    7 

5  10  to   8    9 

*  Calculated  on  the  supposition  that  phosphate  of 
lime  is  worth  Id.  per  lb.;  potash,  2d.,  and  nitrogen  (as 
ammonia)  at  8d. 

f  By  this  is  implied  its  value  as  compared  with  good 
farmyard  manure,  which  has  a  theoretical  value  of 
15s.  7d.,  its  market  value  being  from  5s.  to  7s.  6d.  per 
ton. 


206 

The  old  system  consisted  in  merely 
placing  the  sludge  in  pits,  and  allowing 
it  to  air-dry.  In  this  condition  it  was 
sold  or  given  to  the  farmers.  I  may 
mention  here  that  a  sludge  containing 
90  per  cent,  of  moisture  can  be  reduced 
to  80  per  cent,  by  forty-eight  hours' 
draining,  to  75  per  cent,  by  three  days' 
draining,  and  to  71  per  cent,  after  a 
week's  draining.  After  this,  air  drying 
is  comparatively  slow,  although  no  doubt 
the  admixture  of  porous  substances  would 
render  drying  more  rapid  and  more  com- 
plete. 

III. — DISPOSAL  or  THE  SLUDGE. 
1.  Johnson's  Process.— By  this  pro- 
cess the  liquid  portion  of  the  sludge  is 
extracted  by  pressure  in  a  series  of  com- 
partments. Each  compartment  is  pro- 
vided with  a  canvas  cloth,  which  acts  as  a 
strainer,  and  retains  the  solids  as  the 
liquid  passes  through.  The  sludge  is 
driven  into  the  compartments  by  com- 
pressed air,  100  to  120  Ibs.  per  square 
inch,  until  they  can  hold  no  more.  On 


207 

opening  the  press,  a  solid  cake  of  com- 
pressed sludge  is  found  in  each  compart- 
ment. The  cake  is  compact,  easily 
handled,  and  practically  has  no  smell. 
II  has  a  certain  manurial  value. 

It  is  worth  while  to  consider  a  few 
details  of  pressing.  The  sludge,  as  pre- 
cipitated, contains  on  an  average  90  per 
cent,  of  water,  whilst  the  pressed  sludge 
cake  contains  50  per  cent.  By  simple 
air  drying,  the  50  per  cent,  of  moisture 
may  be  reduced  to  less  than  20  per  cent. 
Thus  in  every  ton  (2,240  Ibs.)  of  un- 
pressed  sludge,  2,016  Ibs.  is  moisture, 
and  224  Ibs.  solid  matter.  After  pressure, 
the  224  Ibs.  of  solid  matter  holds  about 
224  Ibs.  of  moisture,  the  removal  of  1,792 
Ibs.,  or  about  179  gallons,  of  water  hav- 
ing been  effected.  The  time  occupied  in 
the  compression  of  5  tons  is  about  one 
hour.  The  sludge  cake,  according  to 
Monro,  contains  from  0.6  to  0.9  per 
cent,  of  nitrogen,  and  over  1  per  cent,  of 
phosphoric  acid.  It  has  been  the  prac- 
tice to  run  back  the  liquid  expressed 
from  the  sludge  into  the  sewer,  to  be  re- 


208 

treated.  Professor  Dewar  and  myself 
have  pointed  out  that  this  course  is  un- 
advisable.  The  liquid  thus  expressed  is 
exceedingly  foul,  although  perfectly  clear, 
and  does  not  readily  lend  itself  to  ordi- 
nary chemical  precipitation.  I  will  merely 
note  that  it  requires  separate  treatment, 
and  that  our  experiments  indicate  that 
chloride  of  lime  or  perchloride  of  iron  in 
larger  amount  than  is  required  for  ordi- 
nary sewage  may  be  rendered  effective 
for  the  purpose. 

The  manurial  value  of  the  pressed 
sludge  cake  from  Coventry,  Leyton  and 
West  Ham,  has  been  the  subject  of  care- 
ful investigation  by  Dr.  Monro,  from 
whom  I  have  abstracted  the  percentage 
details  of  experiments  on  the  dried 
sludge  given  in  the  following  table  : 


209 


PERCENTAGE  DETAILS  OF  EXPERIMENTS  ON  THE 
DRIED  SLUDGE. 


-332 

QJ    C    C       • 

•gfi 

8|g 

•£  **q  c 

*5  aj  w  3 

•c» 

?  «"§ 

^a^-5 

'O 

^'5^5 

|^| 

8? 

"S  * 

s^og 

"«  B  ^^ 

^I'fr 

I&S2 

tll^ 

02   Q.4J 
Bi| 

•0^3-^ 

§1^ 
|£g§ 

|^S 

cc'C^  fl 

®ra  02  cs 

Organic  matter  

26  14 

26  08 

40  32 

Containing  nitrogen  

1  36 

1  35 

1  82 

Potash  

0  30 

0  34 

0  22 

Total  P-iO&  

2  43 

2  04 

2  57 

Soluble  PaO6  

1.37 

1  69 

1.24 

The  phosphoric  acid  in  sewage  sludge 
is  chiefly  in  combination  with  alumina. 
Dr.  Monro  notes  that  whilst  Coventry 
sewage  contains  much  manufacturing 
refuse  from  dye  works,  and  West  Ham 
sewage  the  refuse  from  industries  of  a 
most  varied  and  polluting  character, 
Leyton  is  a  rural  and  suburban  district, 
having  no  manufactures  of  any  kind  con- 
tributing to  the  sewage. 


210 

Dr.  Monro  has  practically  tested  the 
agricultural  value  of  these  pressed  sludge 
cakes,  for  the  details  of  which  the  reader 
is  referred  to  his  original  paper.  Good 
crops  of  swedes  were  obtained.  The 
three  sludges  gave  almost  identical  re- 
sults as  regards  yield.  The  following 
were  the  results  obtained  by  him  with 
different  dressings  for  comparison  : 

RESULTS  PER  ACRE. 

Tons.  Cwt. 

1.  10  tons  farmyard  manure 13  11^ 

2.  4  cwt.  superphosphate 11  2J 

3.  5  tons  Leyton  sludge 10  4 

4.  5  tons  farmyard  manure 10  1| 

5.  5  tons  West  Ham  sludge 9  8J 

6.  5  tons  Coventry  sludge 9  6^ 

7.  2  cwt.    superphosphate   with  2 

cwt.  of  nitrate 9          5J 

8.  2  cwt.  superphosphate 9          4£ 

9.  2  cwt.  coprolite 8        15£ 

10.  4  cwt.  coprolite 7        10 

11.  Unmanured 5        18 

From  these  details  it  is  evident  that  the 
air-dried  filter- pressed  cake  has  a  certain 
manurial  value — at  any  rate,  about  equal 


211 

to  farmyard  manure — which  possibly, 
considering  how  easily  it  may  be  stored 
without  causing  a  nuisance,  may  be 
worthy  of  being  considered  more  fully 
than  it  has  at  present.  It  is  worth 
noting  that  although  the  newly  pressed 
cake  is  richer  in  nitrogen  than  farmyard 
manure,  and  contains  more  than  double 
the  amount  of  phosphoric  acid,  still  that 
the  manurial  value  is  not  greater,  weight 
for  weight.  This  Dr.  Monro  explains  by 
differences  of  physical  condition,  viz., 
the  loose  texture  of  farmyard  manure 
compared  with  the  compact  condition  of 
the  sludge  cake ;  the  physical  state  of  the 
one  being  as  favorable  to  rapid  oxidation 
and  disintegration  as  that  of  the  other  is 
unfavorable.  To  overcome  this  difficulty, 
Dr.  Monro  suggests  the  reduction  of  the 
cake  to  a  fine  state  of  subdivision. 

The  cost  of  procuring  the  sludge  is 
stated  by  Mr.  Hutchinson  (to  whose  ex- 
cellent paper  I  must  refer)  as  from  2s.  to 
2s.  6d.  per  ton  at  Coventry.  I  have  no 
records  as  to  what  the  further  cost  of 
grinding  would  involve. 


212 

The  Johnson  process  is  at  work  at 
Croyden  Rural,  High  Wycombe,  Cov- 
entry, Ley  ton,  Blackburn,  and  Ayles- 
bury. 

(2.)  Major-  General  Scott's  ^Process. — 
This  is  adopted  at  Burnley.  The  lime 
precipitated  sludge  (i.  e.,  lime  and  or- 
ganic matter)  is  drained  until  it  contains 
about  65  per  cent,  of  moisture.  The 
sludge  at  this  stage  is  tested  as  to  the 
amount  of  lime  present,  more  being 
added  if  necessary.  The  mass  is  now 
dried  by  heat,  and  finally  burnt  in  kilns. 
The  residual  clinker  is  ground,  and  used 
as  an  hydraulic  cement  (Portland  cement). 
The  cement  is  said  to  have  a  tensile 
strength  of  350  Ibs.  per  square  inch  after 
immersion  in  water  for  seven  days,  and 
to  be  worth  35s.  per  ton. 

It  is  evident  that  the  composition  of 
sewage  sludge  varies  not  only  in  differ- 
ent towns,  but  in  the  same  town  at 
different  times.  It  is  not  quite  clear 
how  far  this  process  can  be  worked  so  as 
to  secure  that  which  engineers  know  to 
be  so  important,  viz.,  a  cement  of  con- 


213 

stant  character.  (See  paper  by  Granville 
Cole,  Ph.D.,  Society  of  Arts  Conference, 
1879,  p.  137.) 

The  cost  of  drying  is  7s.  per  ton.  The 
coke  employed  for  burning  averages  Is. 
4d.  per  ton,  and  the  labor,  etc.,  15s.  per 
ton. 

Major  Scott  has  suggested  that  in 
the  case  of  the  London  sewage  both 
a  manure  and  a  cement  might  be  pre- 
pared. 

In  the  Journal  of  the  Society  of  Arts, 
November  28,  1879,  he  suggests,  in  the 
treatment  of  sewage,  that  the  primary 
separation  of  the  coarser  mineral  sus- 
pended matter  should  be  effected  in  a 
first  tank,  a  sufficient  period  of  rest  being 
afterwards  allowed  for  the  subsidence 
(not  the  artificial  precipitation)  of  the 
lighter  suspended  matters  in  a  second 
tank.  The  sludge  of  this  second  tank 
(i.  e.,  after  the  watery  portion  has  been 
drawn  off)  is  to  be  treated  with  about 
two-thirds  its  weight  of  milk  of  lime, 
sufficient  superphosphate  being  after- 
wards added  nearly  to  neutralize  the 


214 

lime.  (The  superphosphate  is  to  be  pre- 
pared by  mixing  20  cwt.  of  Cambridge 
coprolites  with  17  cwt.  of  brown  sul- 
phuric acid,  sufficient  water  being  added 
to  render  the  mixture  almost  fluid).  By 
this  treatment  the  mixture  (he  states) 
becomes  surprisingly  inodorous,  and 
dries  with  rapidity.  The  cost  of  chemi- 
cals he  values  at  16s.  6d.  per  ton  of  pre- 
pared manure,  its  removal  from  the 
tanks  and  subsequent  drying  being  3s. 
6d.  He  considers  it  worth  £3  10s.  per 
ton.  The  sewage  or  liquid  portion  of 
the  second  tank,  from  which  the  organic 
matter  has  been  recovered,  is  then  to  be 
treated  with  lime,  and  the  precipitate 
thus  obtained  made  into  a  cement. 

Major  Scott  seems  to  have  overlooked 
the  difficulty  of  effecting  precipitation  of 
the  suspended  matters  of  sewage  (such 
as  he  is  desirous  of  obtaining  in  the 
second  tank)  without  the  use  of  precipi- 
tants.  Further,  a  limed  sludge,  when 
dried,  is  certain  to  lose  ammonia,  in 
other  words,  is  certain  to  lose  manurial 
value. 


215 

The  deposit  in  the  first  tank  Major 
Scott  proposed  should  be  burnt  in  a  de- 
structor with  waste  cinders,  and  be  used 
to  reclaim  a  portion  of  the  marshes.  At 
any  rate  (he  justly  considers)  it  ought 
not  to  be  allowed  to  pass  into  the  river. 

(3.)  Destructor. — The  destructor  has 
been  carried  to  its  greatest  state  of  per- 
fection at  Baling,  under  the  ingenious 
and  careful  management  of  Mr.  Charles 
Jones.  In  this  case,  however,  the  ashes 
of  the  district  are  mixed  with  the  sludge. 
The  chemicals  used  for  precipitation  are 
11.5  grains  of  clay  and  about  10  grains 
of  lime  per  gallon,  a  little  iron  and 
alumina  being  also  used.  The  sewage 
treated  comes  from  a  population  of  about 
18,000,  and  is  equal  to  600,000  gallons 
daily.  About  157  cubic  yards  of  sludge 
are  obtained  per  week.  This  is  mixed 
with  about  100  cubic  yards  of  ashes  and 
house  refuse.  Before  the  mass  is  burnt 
in  the  destructor,  about  25  per  cent,  of 
the  liquid  portion  is  allowed  to  drain 
away. 

It  may  be  advisable  here  to  note  the 


216 

difficulties  that  have  been  met  with  gen- 
erally in  the  use  of  destructors : 

1.  An  escape  of  vapors  that  prove  more 
or  less  offensive  at  a  considerable  dis- 
tance from  the  shaft.  This  depends  on 
the  materials  having  undergone  incom- 
plete burning,  in  other  words,  that  the 
materials  in  the  destructor  have  been 
subjected  to  destructive  distillation  (in 
which  case  the  products,  consisting  of 
various  empyreumatic  vapors,  are  offens- 
ive), rather  than  combustion,  in  which 
case  the  products  would  be  simply  water 
and  carbonic  acid,  and  inoffensive.  No 
doubt,  until  lately,  the  escape  of  unburnt 
and  partially  burnt  vapors,  a  very  small 
quantity  of  which  sufficed  to  cause  a 
nuisance,  have  proved  a  serious  objection 
to  the  use  of  destructors. 

2.  The  escape  from  the  shaft  of  un- 
burnt or  partially  charred  paper,  fine 
sand,  etc.,  at  certain  stages  of  the  pro- 
cess. 

I  do  not  hesitate  to  say  that  both  of 
these  difficulties  are  met  in  Jones'  de- 
structor. This  has  been  done  by  mixing 


217 

the  sludge  with  the  house  ashes,  thus 
assisting  effective  combustion.  Mr.  Jones 
lays  down  that  every  town  supplies  suffi- 
cient house  refuse  to  burn  its  sludge.  The 
main  point,  however,  on  which  he  relies, 
is  the  construction  of  a  muffle  furnace  (a 
fume  destroyer,  as  he  calls  it)  between 
the  furnace  and  the  main  shaft.  As  a 
result,  not  only  is  a  greatly  increased 
draught  secured,  but  the  combustion  of 
unburnt  vapors  discharged  from' the  fur- 
nace in  which  the  sludge  is  placed  is 
secured.  I  may  add  that  Mr.  Jones  in- 
forms me  that  the  muffle  furnace  is  kept 
going  at  a  cost  of  Is.  6d.  per  day,  but 
that  this,  in  addition,  gives  10  Ibs.  of 
steam  for  engine  purposes.  He  obtains, 
as  a  residuum  from  the  furnace,  25  per 
cent,  of  hard  clinker,  which  is  utilized  in 
various  ways,  viz.,  for  artificial  stone, 
road-making,  etc. 

Various  suggestions  for  what  may  be 
called  fortifying  the  sludge  have  been 
suggested.  Thus,  Colonel  Jones,  of 
Wrexham,  after  drying  the  sludge  to  20 
per  cent,  of  moisture,  adds  to  every  12 


218 

parts  7  parts  of  raw  bone  meal  and  one 
part  of  sulphate  of  ammonia. 

I  do  not  propose  discussing  other  sug- 
gestions for  the  disposal  of  sludge,  such 
as  the  separation  of  the  water  by  centrifu- 
gal machines — converting  the  sludge  into 
a  fuel  by  admixture  with  other  waste 
products — its  conversion  into  a  combus- 
tible gas — making  it  into  bricks,  etc. 
(Monson).  These  suggestions  are  scarcely 
practical. 


The  question  of  cost  must  be  consid- 
ered in  conjunction  with  (1)  the  quantity 
of  the  sewage,  (2)  the  quality  of  the 
sewage  (that  is,  the  nature  of  the  sewage 
other  than  mere  excreta),  (3)  the  flow  per 
head,  and  (4)  the  standard  of  excellence 
required. 

As  regards  quantity,  I  wish  to  say  that 
you  cannot  apply  the  cost  of  treating 
small  volumes  of  sewage  to  the  cost  of 
treating  large  volumes,  the  treatment  of 
the  former  being  more  easily  effected 
than  the  latter. 


219 

PRICES  OF  CHEMICALS. 

Green  copperas  or  proto-sulphate  of 
iron  can  be  obtained  for  about  20s.  per 
ton. 

Lime  can  be  obtained  from  10s.  to  15s. 
per  ton. 

Sulphate  of  alumina  can  be  obtained 
from  46s.  6d.  per  ton,  as  per  following 
analysis : — 

Moisture 5.94 

Crystallized  sulphate  of  alumina. 77.44 

"         sulphate  of  iron 4.00 

Sulphates  of  alkalies  and  sulphuric  acid.     6.82 
Insoluble  iron  and  alumina 5.80 


100.00 

The  annual  cost  of  thoroughly  and 
efficiently  treating  the  sewage  of  Coven 
try,  pressing  the  whole  of  the  sludge 
etc.,  exclusive  of  interest  on  plant,  land, 
and  depreciation — the  population  con- 
tributing being  45,000  persons,  and  the 
sewage  containing  large  quantities  of  dye 
and  manufacturing  refuse — is  £2,800  per 
annum,  an  amount  equal  to  Is.  3d.  per 
head. 


220 

The  cost  at  Hertford,  where  the  sludge 
is  not  pressed,  and  manufacturing  refuse 
is  absent,  with  a  population  of  7,747,  is 
£570  per  annum,  equal  to  Is.  5£d.  per 
head. 


A  few  words  only  on  the  analysis  of 
sewage.  No  single  analysis  of  a  sewage 
effluent  is  satisfactory  as  proof  of  good 
or  of  inefficient  working.  Knowing  as 
we  do  that  sewage  varies  from  hour  to 
hour,  no  accurate  conclusion  can  be 
drawn  as  to  the  composition  of  the  raw 
sewage  or  of  the  effluent,  except  by  col- 
lecting half  hourly,  or  at  least  hourly, 
samples  during  one  entire  period  of 
twenty-four  hours,  and  the  various  sam- 
ples mixed  in  the  proportion  of  the  fluid. 
The  analysis  of  a  sample  of  raw  sewage 
and  of  an  effluent  taken  about  the  same 
time  are  not  comparable,  because  the 
passage  of  the  sewage  through  the  tanks 
is  commonly  the  work  of  some  hours. 
Supposing,  for  example,  I  collect  a  sam- 
ple of  twelve  o'clock  sewage  and  a  sample 


221 

of  effluent  at  the  same  time,  the  twelve 
o'clock  sewage  may  be  the  very  strongest 
sewage  of  the  day;  whilst  the  effluent 
sample  is  the  effluent  of  the  very  weakest 
sewage.  Precisely  the  opposite  condi- 
tion may  occur,  viz.,  that  I  may  compare 
the  effluent  of  the  strongest  sewage  with 
the  weakest  raw  sewage  delivered. 

Further,  in  all  cases  where  analyses 
are  made  for  test  purposes,  the  weather 
should  be  noted,  the  rainfall  and  the  flow 
being  compared  with  the  average  flow. 
For  accurate  purposes  a  normal  condi- 
tion of  flow  should  be  selected,  and  com- 
parison made  between  the  average  of 
twenty-four  hours'  sewage  and  twenty- 
four  hours'  effluent. 


As  regards  the  analysis  of  sewage,  it  is 
advisable  to  estimate  the  quantity  of  the 
matters  in  suspension,  and  in  these  the 
amount  of  mineral  and  organic  (with 
volatile)  matters.  In  addition  to  this, 
I  have  of  late  adopted  the  system  of  esti- 
mating the  organic  carbon  and  nitrogen, 
and  the  oxygen  required  to  oxidize  the 


222 

organic  matter  in  the  effluent  without 
removing  the  suspended  matter.  Seeing 
that  the  real  issue  is  the  condition  of  the 
effluent,  I  consider  this  method  preferable 
to  an  analysis  of  the  clear  effluent  after 
the  removal  of  the  suspended  matter. 

I  propose  the  following  form  as  one 
which  conveys  the  best  information  that 
chemistry  can  afford  as  to  the  chemical 
composition  of  a  sewage  and  of  an 
effluent : — 

The  results  are  stated  in  grains  per  imperial  gal- 
lon of  70,000  grains. 
Matters  in  Suspension — Total .... 
(a)  Organic  and  volatile. . . . 
09)  Mineral 

The  following  details  have  been  obtained  from  the 
effluent  without  the  removal  of  the  suspended 
matters: — 

Total  solids  (suspended  and  dissolved) 

Ammonia 

Chlorine 

=Chloride  of  sodium 

Nitrogen  (as  nitrites  and  nitrates). . . . 
Oxygen  required  to   oxidize   organic 

matter 

Organic  carbon 

Organic  nitrogen 


223 

To  get  rid  of  execretal  filth  with  the 
least  possible  delay  is  no  doubt  the 
teaching  of  sanitary  science.  The  advo- 
cates of  the  water  closet  urge  that  water 
as  a  vehicle  to  carry  the  refuse  commends 
itself  to  us  on  'the  ground  of  conven- 
ience, cleanliness  and  cheapness.  They 
would  compare,  with  plausible  argument, 
the  natural  power  of  gravitation  (such  as 
is  made  use  of  in  the  water  closet)  with 
an  organization  of  men  and  carts  (such 
as  is  required  by  the  dry  earth  system). 
The  advantages,  at  first  sight,  seem  all  on 
one  side.  Facts,  however,  point  in  an 
opposite  direction.  Dilution  with  water 
is  the  best  known  method  of  rendering 
practically  useless  whatever  is  valuable 
in  sewage — indeed,  worse  than  useless, 
an  ungovernable  nuisance.  The  excreta 
of  animals  are  no  doubt  intended  for  the 
food  of  plants,  and  for  our  use  through 
their  intervention.  Of  course,  do  what 
we  will,  nature  will  assert  herself  and  her 
plans.  But  nature  is  embarrassed  by 
our  meddlesomeness.  The  nutritive  food 
of  the  plant  we  drown  in  water,  our  in- 


224 

genuity  failing  when  we  attempt  to  deal 
with  the  filthy  mixture.  We  cannot 
utilize  it,  unless  we  abandon  all  sanitary 
precautions ;  it  pollutes  our  air,  renders 
our  ground  a  stinking  morass,  and  defiles 
our  watercourses.  Thirty  gallons  of 
water  daily  per  head  is  brought  to  us 
who  live  in  London,  from  pure  sources, 
at  great  cost,  and  with  great  engineering 
skill ;  filtered,  often  refiltered,  with  ex- 
traordinary care ;  stored  with  scrupulous 
anxiety;  analyzed  by  one  chemist  after 
another.  It  is,  however,  a  striking  fact 
that  only  l-90th  part  of  the  entire  water 
supply  is  used  for  drinking  purposes,  a 
large  quantity  being  destined  to  become 
the  diluent  of  our  sewage,  to  perplex  us 
by  its  quantity,  to  bother  us  by  its  use- 
lessness,  and  to  steal  our  health  by 
the  perpetual  nuisance  it  occasions. 


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